5 • Applying Fractions Add, subtract, multiply, and divide to solve fraction problems. Key Vocabulary compatible numbers (p. 232) like fractions (p. 236) reciprocal (p. 258) unlike fractions (p. 237) Real-World Link Baking The measurements found on measuring cups and spoons are written as fractions. You will use fractions to find how much of each ingredient is needed when you make part of a whole recipe. Applying Fractions Make this Foldable to help you organize your notes. Begin with a plain sheet of 11” by 17” paper, four index cards, and glue. 1 Fold the paper in half widthwise. 2 Open and fold along 1 the length about 2_” 2 from the bottom. 3 Glue the edge on each side to form two pockets. 4 Label the pockets Fractions and Mixed Numbers, respectively. Place two index cards in each pocket. 228 Chapter 5 Applying Fractions Fractions Mix Numbeed rs GET READY for Chapter 5 Diagnose Readiness You have two options for checking Prerequisite Skills. Option 2 Math Online Option 1 Take the Online Readiness Quiz at glencoe.com. Take the Quick Quiz below. Refer to the Quick Review for help. Example 1 Find the LCD of each pair of fractions. (Lesson 4-8) 5 3 1. _ , _ 5 7 3. 1 8 ,_ _ 15 6 Multiply or divide. 2. _1 , _4 4. 7 _3 , _ 2 5 3 Find the LCD of _ and _ . 6 9 4 10 The LCD is the LCM of the denominators, 6 and 10, or 30. 10 Example 2 (Prior Grade) 5. 1.8 × 12 6. 99 ÷ 12 Find 7.8 ÷ 0.25. 7. 83 ÷ 100 8. 4.6 × 0.3 31.2 0.25 7.80 0 -7 5 _____ 30 -25 ____ 50 -50 ____ 0 9. MEASUREMENT How many 1.6-meter sections of rope can be cut from a length of rope 6.4 meters? (Prior Grade) 10. COINS Manuel owes each of Move the decimal point 2 places to the right and divide as with whole numbers. 8 friends $0.35. How much does he owe in all? (Prior Grade) Complete to show equivalent mixed numbers. (Prior Grade) Example 3 1 11. 3_ = 2 _ 12. mixed numbers. 13. 6_ = 5 _ 4 4 14. 8_ = 7 _ 5 1 15. 5 2 9_ = 3 6 7 _5 3 7 2 RECIPES A recipe calls for 4_ cups 3 of flour. This is equivalent to 3 cups of flour plus an additional how many cups of flour? (Prior Grade) 2 Complete 4_ = 9 11 _ to show equivalent 9 2 2 = 3 + 1_ 4_ 9 9 9 2 =3+_ +_ 9 11 =3+_ 11 = 3_ 9 9 9 Chapter 5 Get Ready for Chapter 5 229 5-1 Estimating with Fractions MAIN IDEA Estimate sums, differences, products, and quotients of fractions and mixed numbers. New Vocabulary MAMMALS The table below lists the average length for a few mammals. 1. Graph 9_ on a number line. To the nearest whole number, 1 4 how long is an American Bison? 2. Graph 3_ on a number line. To the nearest whole number, 3 4 how long is a dingo? compatible numbers Math Online 3. About how much longer is the American bison than a dingo? glencoe.com Mammal • Extra Examples • Personal Tutor • Self-Check Quiz Length (ft) Brown Bear 6_ American Bison 9_ Opossum 2_ Dingo 3_ 1 2 1 4 1 2 3 4 To estimate the sum, difference, product, or quotient of mixed numbers, round the mixed numbers to the nearest whole number. 9 1 1 94 92 Round down. 9 _41 ≈ 9 3 94 10 Round up. 9 _21 ≈ 10, 9 _43 ≈ 10 Estimate with Mixed Numbers _ _ _ _ 1 Estimate 3 2 + 5 1 . 2 Estimate 6 2 × 1 7 . 2 _ 3_ + 51 ≈ 4 + 5 or 9 3 6 5 8 2 7 6_ × 1_ ≈ 6 × 2 or 12 5 8 The sum is about 9. The product is about 12. 3 6 Estimate. a. 2_ + 3_ 1 5 230 Chapter 5 Applying Fractions 1 2 b. 4_ × 5_ 3 8 1 4 c. 8_ ÷ 2_ 7 9 3 4 To estimate the sum, difference, product, or quotient of fractions, 1 , or 1, whichever is closest. Number lines round each fraction to 0, _ 2 and fraction models, like the ones shown below, can help you decide how to round. Fractions Close to 0 0 1 6 Fractions Close to 1 _1 1 5 2 8 0 1 7 Fractions Close to 1 2 9 10 1 0 1 4 9 5 6 The numerator is much The numerator is about half of smaller than the denominator. the denominator. The numerator is almost as large as the denominator. Estimate with Fractions _ _ 3 Estimate 1 + 2 . 8 3 1 is much smaller than 8, so 2 is close to half of 3, so Estimating with Fractions If one of the fractions is a mixed number, such as 5 2 , round the 3_ +_ 3 8 _1 ≈ 0. 8 _2 ≈ _1 . 3 2 _1 + _2 ≈ 0 + _1 = _1 The sum is about _1 . 8 3 2 2 2 _ _ 4 Estimate 6 - 7 . 7 mixed number to the nearest whole number and the fraction to the 10 5 2 ≈ nearest half. 3 _ +_ 3 8 4 + _21 or about 4_21 . 6 is almost as large as 7, so 6 7 1 0 1 2 0 7 10 7 is about half of 10, so 1 7 1 1 _6 - _ ≈1-_ =_ 7 2 10 _6 ≈ 1. 7 _7 ≈ _1 . 10 2 1 The difference is about _ . 2 2 _ _ 5 Estimate 8 ÷ 5 . 9 6 _8 ≈ 1 and _5 ≈ 1. _8 ÷ _5 ≈ 1 ÷ 1 = 1 9 9 6 6 The quotient is about 1. Estimate. d. _1 + _3 7 5 e. _7 - _5 8 9 f. 11 _3 × _ 5 12 g. _7 ÷ _2 8 5 Lesson 5-1 Estimating with Fractions 231 Compatible numbers, or numbers that are easy to compute mentally, can also be used to estimate. Use Compatible Numbers Estimate using compatible numbers. _ 6 1 · 14 THINK What is 3 _1 · 14 ≈ _1 · 15 or 5 3 3 _1 of 14? 3 Round 14 to 15, since 15 is divisible by 3. _1 of 15 is 15 ÷ 3 or 5. 3 _ _ 7 97 ÷ 41 Compatible Numbers When dividing mixed numbers, round so that the dividend is a multiple of the divisor. 5 8 7 1 1 9_ ÷ 4_ ≈ 10 ÷ 4_ 8 5 5 _7 8 1 _ Round 4 to 5, since 10 is divisible by 5. Round 9 to 10. ≈ 10 ÷ 5 or 2 5 Estimate using compatible numbers. h. _1 · 21 i. 4 _1 · 17 j. 12 ÷ 6_ 2 3 3 8 MONSTER TRUCKS The height of the wheels on the monster truck at _ the left is about 2 of the total height of the truck. Estimate the 3 height of the wheels. Real-World Link The monster truck 1 shown is 15_ feet tall 2 and weighs 28,000 pounds. Words 2 Wheel height is _ of the truck height. Variable Let x represent the wheel height. 3 Equation x 2 x≈_ · 15 Round 15 to 15, 3 x ≈ 10 = 2 _ 3 · _1 15 2 _1 2 since 15 is divisible by 3. _1 of 15 is 5, so _2 of 15 3 3 is 2 · 5 or 10. Source: Monster Trucks UK The wheels are about 10 feet high. k. MEASUREMENT The area of a rectangle is 19_ square feet. The width 3 4 1 of the rectangle is 5_ feet. What is the approximate length of the 4 rectangle? 232 Chapter 5 Applying Fractions Examples 1–5 (p. 230–231) Estimate. 1. 8_ + 1_ 3 8 5. Examples 6, 7 (p. 232) Example 8 (p. 232) HOMEWORK For Exercises 12–19 20–29 30–35 HELP See Examples 1, 2 3–5 6–8 2. 2_ - 1_ 5 6 4 5 _1 + _2 6 6. 5 3. 5_ · 2_ 5 7 1 8 _6 - _1 7 7. 5 4. 9_ ÷ 2_ 7 8 2 7 _5 · _8 8 8. 9 2 3 _4 ÷ _6 5 7 Estimate using compatible numbers. 9. _1 · 15 10. 21_ ÷ 9_ 5 6 4 2 3 4 6 5 ft 11. BIRDS A seagull’s wingspan is about _ of a bald 2 3 eagle’s wingspan. The eagle’s wingspan is shown at the right. Estimate the wingspan of a seagull. Estimate. 12. 3_ + 4_ 13. 1_ + 5_ 14. 5_ - 3_ 1 6 15. 4_ - 1_ 16. 2_ · 6_ 17. 1_ · 3_ 18. 6_ ÷ 1_ 19. 8_ ÷ 2_ 3 4 5 6 2 3 1 8 1 3 11 12 4 5 1 3 1 4 1 8 2 3 2 5 1 2 5 8 1 2 20. _3 + _3 21. _5 + _3 22. _5 - _1 23. _3 - _3 24. _1 · _3 25. 11 _4 · _ 26. _4 ÷ _7 27. 5 1 _ ÷_ 8 4 8 4 8 9 7 12 9 6 5 8 28. COOKING Joaquim wants to make the macaroni and cheese shown at the right, but 3 he has only about 1_ cups of macaroni. About 4 how much more macaroni does he need? 29. MEASUREMENT Isabella is sewing a trim that 1 is 1_ inches wide on the bottom of a skirt 5 4 6 10 Macaroni $ Cheese 3 tbsp butter 2 21 c uncooked macaroni 1 tbsp salt 1 4 tbsp pepper 1 qt milk 1 2 lb cheese 8 7 inches long. Approximately how that is 15_ 8 long will the skirt be? Estimate using compatible numbers. 30. _1 · 39 31. 4 _1 · 37 32. 23_ ÷ 3 2 9 6 33. 25_ ÷ 5_ 3 10 2 3 34. MONEY Arleta has $22. She uses _ of her money to buy a pair of earrings. 1 3 About how much money did she spend on the earrings? 35. SNACKS A cereal company has 24 pounds of granola to package in bags that 3 contain 1_ pounds of granola. About how many bags will they have? 4 Lesson 5-1 Estimating with Fractions 233 36. FIND THE DATA Refer to the Data File on pages 16–19. Choose some data and write a real-world problem in which you would estimate with fractions. 37. SPORTS Paquito and Jeff are on a basketball team. The table shows the approximate fraction of the team’s points that each of them scored in a game. If the team scored a total of 72 points, about how many did Paquito and Jeff score together? Fraction of Total Points Scored Player’s Names Paquito 3 8 Jeff 1 6 38. RESEARCH Research the statistics of any basketball team. How can you use fractions to analyze the statistics? 39. COOKING Kathryn baked the sheet of Real-World Link The femur or thigh bone is the longest in length, largest in volume, and strongest bone of the human body. . 7 in 7 8 brownies shown. She wants to cut it into brownies that are about 2 inches square. How many brownies will there be? 12 3 in 8 . ANALYZE TABLES For Exercises 40–43, use the following information and the table shown. The adult human skeleton is made up of 206 bones. The table shows the approximate fraction of the bones that each body part(s) makes up. Body Part(s) Fraction of Total Bones Feet 1 4 40. About how many bones are in the feet? Hands & Feet 1 2 41. About how many bones are in both hands and feet? EXTRA PRA CTICE See pages 679, 708. H.O.T. Problems 42. About how many bones are in one hand? 43. The length of your thighbone is equal to _ of your height. 1 4 About how many inches long is your thighbone? 44. CHALLENGE In a division expression, the divisor is rounded up and the dividend is rounded down. How does the new quotient compare to the original quotient? Explain. 45. OPEN ENDED Select two fractions whose estimated difference and product 1 . Justify your selection. is _ 2 46. NUMBER SENSE Decide which of the following have sums that are less than 1. Explain. a. _1 + _2 5 3 7 _ _ b. +1 8 2 234 Chapter 5 Applying Fractions c. _5 + _2 d. _1 + _3 6 7 3 9 47. SELECT A TECHNIQUE To make the crust for a peach cobbler, Dion needs 1 2 2 cups of flour, 1_ cups of sugar, and 1_ cups of hot water. He needs to 3_ 3 4 3 mix all of these in a large bowl. The largest bowl he can find holds 6 cups. Which of the following techniques might Dion use to determine whether he can use this bowl to mix the ingredients? Justify your selection(s). Then use the technique(s) to solve the problem. mental math 48. number sense estimation WR ITING IN MATH Explain when estimation would not be the best method for solving a problem. Then give an example. 49. SHORT RESPONSE A chef has 15_ cups 2 3 50. On a full tank of gasoline, a certain car 1 of penne pasta and 22_ cups of rigatoni can travel 360 miles. The needle on its gasoline gauge is shown. Without refueling, which is the best estimate of how far the car can travel? 4 pasta. About how much pasta is there altogether? A 150 miles B 180 miles C 240 miles GAS GAUGE D 329 miles Replace each ● with <, >, or = to make a true sentence. 51. 7 2_ ● 2.75 8 52. -1 -7 _ ●_ 3 3 53. (Lesson 4-9) _5 ● _4 7 5 54. 3_ ● 3_ 6 11 9 14 55. SHOPPING A store sells a 3-pack of beaded necklaces and a 5-pack of beaded bracelets. How many packages of each must you buy so that you have the same number of necklaces and bracelets? (Lesson 4-8) Write each decimal as a percent. 56. 0.56 57. 0.375 (Lesson 4-7) 58. 0.07 59. 0.019 PREREQUISITE SKILL Find the LCD of each pair of fractions. 60. 5 _3 , _ 4 12 61. 7 _1 , _ 2 10 62. _1 , _1 6 8 (Lesson 4-9) 63. _4 , _2 5 3 Lesson 5-1 Estimating with Fractions 235 5-2 Adding and Subtracting Fractions MAIN IDEA Add and subtract fractions. New Vocabulary like fractions unlike fractions INSTANT MESSENGER Sean surveyed ten classmates to find which abbreviation they use most when they instant message. Abbreviation Number L8R 5 LOL 3 BRB 2 1. What fraction uses L8R? BRB? 2. What fraction uses either L8R or BRB? Math Online glencoe.com • Extra Examples • Personal Tutor • Self-Check Quiz • Reading in the Content Area Fractions that have the same denominators are called like fractions. Key Concept Add and Subtract Like Fractions Words To add or subtract like fractions, add or subtract the numerators and write the result over the denominator. Examples Numbers Algebra 5 +2 7 _5 + _2 = _ or _ a+b _ac + _bc = _ c , where c ≠ 0 11 4 11 - 4 7 _ - _ = _ or _ a-b _ac - _bc = _ c , where c ≠ 0 10 12 10 12 10 12 10 12 Add and Subtract Like Fractions _ _ 1 Add 5 + 2 . Write in simplest form. 9 9 5+2 _5 + _2 = _ 9 9 9 7 _ = 9 Write the sum over the denominator. _ _ 10 10 9 9 1 1 _-_ = _ Subtract the 10 10 10 numerators. 10 _ =4 5 a. 236 Chapter 5 Applying Fractions _1 + _3 6 6 Add the numerators. 2 Subtract 9 - 1 . Write in simplest form. 8 =_ Write the difference over the denominator. 8 10 Simplify. b. 9 10 _3 - _1 7 7 - 1 10 Review Vocabulary LCD the least common multiple of the denominators of two or more fractions; To add or subtract unlike fractions, or fractions with different denominators, rename the fractions using the LCD. Then add or subtract as with like fractions. Example: the LCD of _ 1 4 Add and Subtract Unlike Fractions 2 and _ is 12. (Lesson 4-9) 3 _ _ 3 Add 1 + 1 . Write in simplest form. 2 Estimate 6 METHOD 1 _1 + 0 = _1 2 2 Use a model. _1 2 1 +_ 6 ____ _4 or _2 6 3 METHOD 2 Use the LCD. 1 1 The least common denominator (LCD) of _ and _ is 6. 2 6 Rename using the LCD, 6. Renaming Fractions To rename a fraction, multiply both the numerator and the denominator of the original fraction by the same number. By doing so, the renamed fraction has the same value as the original fraction. 1×3 _ = 2×3 _1 2 1 +_ 6 ____ 2 6 Check for Reasonableness 3 _3 _3 6 1 +_ 6 ____ 4 _ or _2 6 3 6 1 = +_ 6 ____ 1×1 _ 6×1 1 1 2 So, _ +_ =_ . Add. 2 1 _ ≈_ ✔ 3 2 _ _ 4 Subtract 11 - 3 . Write in simplest form. 12 Estimate 8 1-_=_ 1 2 1 2 Since 12 = 22 · 3 and 8 = 23, the LCM of 12 and 8 is 23 · 3 or 24. Rename each fraction using a denominator of 24. Then subtract. Think: 12 Think: 8 11 × 2 22 × 2 = 24, so _ or _. 24 12 × 2 3×3 3 9 × 3 = 24, so _ =_ or _. 24 8 8×3 11 × 2 3×3 3 11 _ -_ =_ -_ . 12 × 2 8 12 The LCD of _ and _ is 24. 9 22 =_ -_ 24 13 =_ 24 Rename the fractions using LCD, 24. 24 Subtract the fractions. 1 13 _ ≈_ ✔ 2 24 Check for Reasonableness c. _8 - _2 9 3 3 8 11 12 8×3 d. _5 - _3 6 8 e. _7 + _3 8 4 Lesson 5-2 Adding and Subtracting Fractions 237 Healthy Lunch SURVEYS In a recent survey, students were asked what they would choose for a healthy lunch. The results are shown in the graph. /POF PGUIFTF 5 What fraction more 25 9×5 3×4 9 3 _ -_ =_ -_ 20 $IJDLFO OVHHFUT 1J[[B of the students chose salad bar rather than a deli sandwich? Key Words The phrase what fraction more suggests subtraction. 4BMBE #BS #VSHFS 'SJFT %FMJ TBOEXJDI The LCD of _9 and _3 is 100. 20 25 20 × 5 25 × 4 45 12 =_ -_ Rename the fractions using the LCD. 100 100 33 =_ Subtract the numerators. 100 33 So, _ more students chose salad bar rather than a deli sandwich. 100 6 What fraction of students chose pizza or chicken nuggets? 3 3 1 2 _ +_ =_ +_ 20 10 20 5 =_ 20 1 =_ 4 20 Rename. Add. Simplify. 1 So, _ of the students chose pizza or chicken nuggets combined. 4 f. SURVEYS What fraction more of the students chose a deli sandwich rather than a burger and fries? Examples 1–4 (pp. 236–237) Add or subtract. Write in simplest form. 1. _4 + _2 9 9 1 _ _ 5. +3 6 8 Examples 5, 6 (p. 238) 2. _5 + _4 3. 6 9 2 _ _ 6. +5 3 6 _3 - _1 8 8 5 _ _ 7. - 7 6 12 4. _4 - _2 8. _3 - _1 5 4 5 3 For Exercises 9 and 10, choose an operation to solve each problem. Explain your reasoning. Then solve the problem. 9. MEASUREMENT Cassandra cuts _ inch off the top of a photo and _ inch off 5 16 3 8 the bottom. How much smaller is the total height of the photo now? 10. CHORES A bucket was _ full with soapy water. After washing the car, the 7 8 1 full. What part of the water was used? bucket was only _ 4 238 Chapter 5 Applying Fractions HOMEWORK For Exercises 11–14 15–22 23–26 HELP See Examples 1, 2 3, 4 5, 6 Add or subtract. Write in simplest form. 11. _3 + _1 12. _5 + _7 13. _5 - _1 14. 3 7 _ -_ 15. 3 1 _ +_ 16. 7 7 _ +_ 17. 11 _5 + _ 18. _7 + _5 19. _7 - _1 20. _4 - _1 21. 2 _4 - _ 22. 3 1 _ -_ 7 7 5 15 9 3 8 8 12 10 5 6 6 8 9 6 12 15 10 10 9 6 10 4 For Exercises 23–26, choose an operation to solve each problem. Explain your reasoning. Then solve the problem. 23. MEASUREMENT Ebony is building a shelf to hold the two boxes shown. What is the smallest width she should make the shelf? 4 5 ft 3 4 ft 24. WEATHER Using the information under the photo, find the difference of the average precipitation for Boise in February and November. 25. MEASUREMENT Makayla bought _ pound of ham and _ pound of turkey. 5 8 1 4 How much more turkey did she buy? 26. ANIMALS The three-toed sloth can travel _ miles per hour while a giant 3 20 17 miles per hour. How much faster, in miles per hour, tortoise can travel _ 100 is the giant tortoise? Simplify. Real-World Link The average precipitation for February and November for Boise, 4 7 Idaho, is _ and _ 10 10 inches, respectively. 27. 5 _1 + _1 + _ 7 2 31. 1 + _ 1 4 28 28. 7 _1 + _5 + _ 6 4 32. 1 - _ 5 8 12 29. ( ) _1 + _2 - _1 6 3 4 30. 33. 2 + _ ( ) _5 - _1 + _1 6 2 3 34. 3 - _ 2 3 1 6 35. MONEY Chellise saves _ of her allowance and spends _ of her allowance at 1 5 2 3 the mall. What fraction of her allowance remains? Source: The Weather Channel 36. ANALYZE TABLES Pepita and Francisco each spend an equal amount of time on homework. The table shows the fraction of their time they spend on each subject. Determine the missing fraction for each student. Homework Pepita Francisco Math English Science _ Fraction of Time _2 3 _1 6 _1 2 _3 8 _ ALGEBRA Evaluate each expression if a = 3 and b = 5 . 37. _1 + a 2 38. b - _ 7 10 4 39. b - a 6 40. a + b Lesson 5-2 Adding and Subtracting Fractions 239 41. BOOK REPORTS Four students were scheduled to give book reports in a 2 hour remained. If the next two 1-hour class period. After the first report, _ 3 1 1 hour and _ hour, respectively, what fraction of the students’ reports took _ 6 4 hour remained after the final students’ report? Justify your answer. 42. MEASUREMENT Mrs. Escalante was riding a bicycle on a bike path. After 3 2 of a mile, she discovered that she still needed to travel _ of a mile riding _ 3 4 to reach the end of the path. How long is the bike path? 43. CELL PHONES One hundred sixty How Do You Use a Cell Phone? cell phone owners were surveyed. What fraction of owners prefers using their cell phone for text messaging or taking pictures? Taking Text pictures messaging 3 3 8 8 44. MEASUREMENT LaTasha and Eric are 1 Playing 4 games 1 jogging on a track. LaTasha jogs _ of a 4 5 of a mile and then stops. Eric jogs _ 8 EXTRA mile, stops and then turns around and PRACTICE 1 jogs _ of a mile. Who is farther ahead 2 See pages 679, 708. H.O.T. Problems on the track? How much farther? 45. CHALLENGE Fractions, such as _ or _, whose numerators are 1, are called 1 2 1 3 unit fractions. Describe a method you can use to add two unit fractions 1 1 +_ . mentally. Explain your reasoning and use your method to find _ 99 100 46. OPEN ENDED Provide a counterexample to the following statement. 1 The sum of three fractions with odd numerators is never _ . 47. 3 1 FIND THE ERROR Meagan and Lourdes are finding _ +_ . 5 4 2 Who is correct? Explain. 1+3 _1 + _3 = _ 4 5 4+5 1x5 _ _1 + _3 = _ + 3x4 4 Meagan 48. 5 4x5 5x4 Lourdes WR ITING IN MATH To make a cake, Felicia needs 1 cup of flour but she 3 2 -measuring cup and a _ -measuring cup. Which method will only has a _ 3 4 bring her closest to having the amount of flour she needs? Explain. a. Fill the _ -measuring cup twice. 2 3 3 _ c. Fill the -measuring cup twice. 4 240 Chapter 5 Applying Fractions b. Fill the _ -measuring cup once. 2 3 3 _ d. Fill the -measuring cup once. 4 49. The table gives the number of hours 50. Which of the following is the prime Orlando spent at football practice for one week. Day factored form of the lowest common 7 11 denominator of _ +_ ? 12 Time (hours) 1 Monday Tuesday _1 F 2×3 2 G 2 × 32 2 1 2_ 3 5 _ 1 6 1 2_ 2 3 _ 1 Wednesday Thursday Friday Saturday 18 H 22 × 32 23 × 3 J 51. Find _ - _. 5 6 4 1 8 4 A _ How many more hours did he practice over the last three days than he did over the first three days? 7 3 B _ 8 1 h A _ 7 C _ 4 12 1 B _ h 17 D _ 2 24 2 C _ h 3 3 D _ h 4 Estimate. (Lesson 5-1) 6 5 52. _ - _ 7 12 53. 4_ + 3_ 3 4 1 9 54. 16_ ÷ 8_ 2 3 55. 5_ · 3_ 1 5 4 5 56. WEATHER The table shows about how much rain falls in Albuquerque and Denver. Which city has the greater fraction of inches of rain per day? Explain. (Lesson 4-9) 57. Write 0.248 as a percent. (Lesson 4-7) ALGEBRA Find each sum if a = -3 and b = 2. 58. a + b 1 3 City Amount of Rain (in.) Number of Days Albuquerque, NM 9 60 Denver, CO 15 90 Source: The Weather Channel (Lessons 2-4 and 2-5) 59. a - b 60. b - a PREREQUISITE SKILL Complete. 61. 5_ = 5 + 2 3 62. 1 = _ 9 63. 1 = _ 5 64. 3 =4+_ 8 Lesson 5-2 Adding and Subtracting Fractions 241 5-3 Adding and Subtracting Mixed Numbers MAIN IDEA Add and subtract mixed numbers. Math Online BABIES The birth weights of several babies in the hospital nursery are shown. Birth Weight (pounds) glencoe.com 8_ 1 8 15 7_ 16 13 _ 6 16 7 5_ 8 Jackson • Extra Examples • Personal Tutor • Self-Check Quiz Nicolás Rebekah Mia 1. Write an expression to find how much more Nicolás weighs than Mia. 2. Rename the fractions using the LCD. 3. Find the difference of the fractional parts of the mixed numbers. 4. Find the difference of the whole numbers. 5. MAKE A CONJECTURE Explain how to find 7_ - 5_. Then use your conjecture to find the difference. 15 16 7 8 To add or subtract mixed numbers, first add or subtract the fractions. If necessary, rename them using the LCD. Then add or subtract the whole numbers and simplify if necessary. Add and Subtract Mixed Numbers _ _ 1 Find 7 4 + 10 2 . Write in simplest form. 9 9 Estimate 7 + 10 = 17 _ 9 2 + 10_ 9 ______ 6 2 _ 17 or 17_ 74 3 9 Add the whole numbers and fractions separately. Simplify. _2 ≈ 17 ✔ Check for Reasonableness 17 a. 6_ + 2_ 1 8 242 Chapter 5 Applying Fractions 5 8 3 b. 5_ + 2_ 1 5 3 10 c. 1_ + 4_ 5 9 1 6 _ _ 2 Find 8 5 - 2 1 . Write in simplest form. 6 3 Estimate 9 - 2 = 7 5 8_ 5 8_ 6 6 1 -2_ 3 _____ 2 -2_ Rename the fraction using the LCD. Then subtract. 6 _____ 3 1 6_ or 6_ 6 2 Simplify. _1 ≈ 7 ✔ Check for Reasonableness 6 2 Subtract. Write in simplest form. d. 5_ - 1_ e. 13_ - 9_ 3 4 f. 8_ - 2_ g. 7_ - 4_ h. 11_ - 3_ i. 9_ - 5_ 3 10 4 5 3 4 Improper Fractions An improper fraction has a numerator that is greater than or equal to the denominator. Examples of improper fractions are _5 and 2 _6 . 5 4 7 8 5 6 1 3 2 3 1 8 4 7 1 2 1 2 Sometimes when you subtract mixed numbers, the fraction in the first mixed number is less than the fraction in the second mixed number. In this case, rename the first fraction as an improper fraction in order to subtract. Rename Mixed Numbers to Subtract _ _ 3 Find 2 1 - 1 2 . 3 3 _1 = _1 Estimate 2 - 1 2 2 1 2 1 Since _ is less than _ , rename 2_ before subtracting. 3 3 3 _3 Change 1 to . 3 _ 21 1 2_ 3 2 -1_ 3 _____ _ _ _ 1 3 + 1 or 1 4 = 3 3 3 3 4 1 4 1_ Rename 2_ as 1_. 3 3 3 2 -1_ 3 _____ _2 3 Subtract the whole numbers and then the fractions. Check for Reasonableness _2 ≈ _1 ✔ 3 2 Lesson 5-3 Adding and Subtracting Mixed Numbers 243 _ 4 Find 8 - 3 3 . Estimate 8 - 4 = 4 4 0 Using the denominator of the fraction in the subtrahend, 8 = 8_ . 4 0 3 is less than _ , rename 8 before subtracting. Since _ 4 4 Rename 8 as 7 + 4 or 7 . Subtract. Check for Reasonableness 4 j. 11_ - 2_ 2 5 k. 5_ - 4_ 3 5 3 8 planner is designing a skateboard park. What will be the length of the park and the parking lot combined? _1 ≈ 4 ✔ 4 l. 7 - 1_ 11 12 1 2 5 MEASUREMENT An urban Real-World Career How Does an Urban Planner Use Math? An urban planner uses math to measure and draw site plans for future development. 4 4 4 3 -3_ 4 ____ _ 41 4 3 -3_ 4 _____ _4 _ 4 7_ 8 1 40 3 ft 1 120 2 ft 3 1 1 2 120_ + 40_ = 120_ + 40_ 2 3 6 5 = 160 + _ 6 6 5 = 160_ 6 Math Online 5 feet. The total length is 160_ For more information, go to glencoe.com. 6 m. MEASUREMENT Jermaine walked 1_ miles on Saturday and 2_ miles 5 8 1 2 on Sunday. How many more miles did he walk on Sunday? Examples 1–4 (pp. 242–244) Example 5 (p. 244) Add or subtract. Write in simplest form. 1. 1_ + 8_ 5 1 7 7 3 1 5. 3_ - 1_ 4 4 1 4 2 5 3 2 6. 5_ - 2_ 3 5 3. 7_ - 3_ 5 6 1 6 3 7. 11 - 6_ 8 4. 9_ - 2_ 3 4 5 8. 16 - 5_ 6 4 5 9. CARS A hybrid car’s gas tank can hold 11_ gallons of gasoline. It contains 9 10 3 gallons of gasoline. How much more gasoline is needed to fill the tank? 8_ 4 244 2. 8_ + 3_ Chapter 5 Applying Fractions HOMEWORK For Exercises 10–17 18–23 24–25 26–29 HELP See Examples 1, 2 3 4 5 Add or subtract. Write in simplest form. 10. 2_ + 7_ 11. 3_ + 4_ 3 2 7 7 3 1 _ 15. 11 - 4_ 3 4 3 1 _ _ 19. 6 - 2 4 4 5 1 _ 23. 12 - 6_ 2 8 1 4 9 9 3 4 _ _ 14. 9 - 2 5 10 3 1 18. 9_ - 2_ 5 5 1 1 _ 22. 14 - 7_ 6 3 12. 10_ - 2_ 13. 8_ - 6_ 6 5 7 7 1 3 _ 17. 8 + 10_ 8 3 3 3 _ _ 21. 4 -1 10 4 5 _ 25. 13 - 5 6 4 1 5 5 5 1 _ 16. 8 + 11_ 12 4 3 2 _ _ 20. 6 - 1 5 3 2 _ 24. 8 - 3 3 For Exercises 26–29, choose an operation to solve each problem. Explain your reasoning. Then solve the problem. 26. HIKING If Sara and Maggie hiked both of the trails listed in the table, how far did they hike altogether? 27. JEWELRY Margarite made Trail Length (mi) Woodland Park 2 3_ Mill Creek Way 2_ 3 5 6 1 7 4 in. the jewelry shown at the right. 5 inches If the necklace is 10_ 8 longer than the bracelet, how long is the necklace that Margarite made? bracelet necklace 28. GARDENS The length of Kasey’s garden is 4_ feet. Find the width of Kasey’s 5 8 7 feet shorter than the length. garden if it is 2_ 8 29. HAIRSTYLES Before Alameda got her haircut, the length of her hair 3 1 inches. After her haircut, the length was 6_ inches. How many was 9_ 2 4 inches did she have cut? Add or subtract. Write in simplest form. 30. 10 - 3_ 31. 24 - 8_ 5 11 3 4 32. 6_ + 1_ + 5_ 1 6 5 9 2 3 33. 3_ + 2_ - 4_ 1 4 5 6 1 3 34. TIME Karen wakes up at 6:00 a.m. It takes her 1_ hours to shower, get 1 4 1 hour to eat breakfast, brush her dressed, and comb her hair. It takes her _ 2 teeth, and make her bed. At what time will she be ready for school? MEASUREMENT Find the perimeter of each figure. 35. 3 EXTRA PRACTICE See pages 680, 708. 3 2 8 yd 2 8 yd 3 2 8 yd 1 5 3 in. 36. 2 4 3 in. 1 3 6 in. 5 4 6 in. Lesson 5-3 Adding and Subtracting Mixed Numbers 245 H.O.T. Problems 37. NUMBER SENSE Which of the following techniques could be used to 3 4 1 7 +_ is greater than, less than, or equal to 2_ + 6_ ? determine whether 6_ 4 5 9 8 Justify your selection(s). Then use the technique(s) to solve the problem. number sense mental math estimation 38. CHALLENGE A string is cut in half. One of the halves is thrown away. One fifth of the remaining half is cut away and the piece left is 8 feet long. How long was the string initially? Justify your answer. 39. WR ITING IN MATH The fence of a rectangular garden is constructed from 5 feet long. 12 feet of fencing wire. Suppose that one side of the garden is 2_ 12 Explain how to find the length of the other side. 40. The distance from home plate to the 41. A recipe for party mix calls for 3 4_ cups of cereal. The amount of pitcher’s mound is 60 feet 6 inches and from home plate to second base is 127 4 2 cups less than peanuts needed is 1_ 3 3 feet 3_ inches. Find the distance from the amount of cereal needed. How many cups of peanuts and cereal are needed? 8 the pitcher’s mound to second base. 1 in. A 68 ft 3_ 2nd base 4 3 B 67 ft 8_ in. 4 5 C 67 ft 2_ in. 8 3 D 66 ft 9_ in. 8 1 cups F 3_ 12 1 cups G 6_ 2 5 cups H 7_ 6 1 cups J 8_ 2 Pitcher’s mound Home plate 42. SCHOOL Kai did _ of her homework in class and _ more of it on the bus. 1 5 1 3 What fraction of homework does she still need to do? Estimate. 43. (Lesson 5-1) 9 _8 ÷ _ 9 (Lesson 5-2) 44. 3_ + 6_ 1 2 10 45. 8_ × 7_ 2 3 4 5 46. 4_ - 1_ 1 9 2 9 1 4 47. MEASUREMENT To carpet a living room with a length of 17 feet, 255 square feet of carpet is needed. Find the width of the living room. (Lesson 3-6) 48. PREREQUISITE SKILL Andre needs to be at the train station by 5:30 p.m. It 1 1 hour to pack and 1 _ hours to get to the station. Find the latest takes him _ 3 4 time he should begin packing. Use the work backward strategy. 246 Chapter 5 Applying Fractions (Lesson 3-4) 5 Mid-Chapter Quiz Lessons 5-1 through 5-3 1. MONEY Latisha spends _ of her money on 3 4 a birthday present for her brother. If she has $33, estimate the amount she spends on her brother’s present. (Lesson 5-1) Estimate. 18. MULTIPLE CHOICE The table shows the weight of a newborn infant for the first year. (Lesson 5-3) Month Weight (lb) 0 7 _1 4 1 _ 12 2 5 _ 16 8 4 _ 19 5 3 _ 23 (Lesson 5-1) 2. 5_ + 1_ 1 7 9 8 5 11 4. _ - _ 20 8 3 4 _ 6. 7 ÷ 1_ 5 4 3. 13_ ÷ 7_ 3 5. 4_ × 1_ 6 1 2 3 4 8 13 _ _ 7. +2 9 15 2 9 2 3 9 12 8. MULTIPLE CHOICE Mrs. Ortega is making 5 batches of muffins for the school bake sale. 1 1 Each batch uses 2_ cups sugar and 1_ cups 2 4 milk. Which is the best estimate of the total amount of sugar and milk Mrs. Ortega uses for the muffins? (Lesson 5-1) A less than 15 cups 20 During which three-month period was the infant’s weight gain the greatest? F 0–3 months H 6–9 months G 3–6 months J 9–12 months 19. MEASUREMENT How much does a 50_ - 1 4 7 pounds is pound suitcase weigh after 3_ 8 removed? (Lesson 5-3) B between 15 and 20 cups C between 20 and 25 cups D more than 25 cups 20. MULTIPLE CHOICE The table gives the Add or subtract. Write in simplest form. average annual snowfall for several U.S. cities. (Lesson 5-3) (Lesson 5-2) 9. 11 1 _ -_ 15 15 1 2 11. _ + _ 2 9 10. 3 4 _ -_ 7 14 5 3 12. _ + _ 8 4 39 13. SCIENCE _ of Earth’s atmosphere is made 50 21 is made up of up of nitrogen while only _ 100 oxygen. What fraction of Earth’s atmosphere is either nitrogen or oxygen? (Lesson 5-2) Add or subtract. Write in simplest form. (Lesson 5-3) 14. 8_ - 2_ 3 5 4 12 5 2 16. 2_ + 1_ 9 3 15. 5_ - 1_ 1 1 6 3 3 13 _ _ 17. 2 + 6 5 15 City Average Snowfall (in.) _4 Anchorage, AK 70 Mount Washington, NH 259 Buffalo, NY Birmingham, AL 5 _9 10 _3 5 1 _ 1 93 2 Source: Fact Monster On average, how many more inches of snow does Mount Washington, New Hampshire, receive than Anchorage, Alaska? 7 A 330_ in. 10 _ B 189 1 in. 10 3 C 166_ in. 10 1 D 92_ in. 10 Chapter 5 Mid-Chapter Quiz 247 Problem-Solving Investigation 5-4 MAIN IDEA: Solve problems by eliminating possibilities. e–Mail: ELIMINATE POSSIBILITIES MADISON: I am making school pennants to decorate 1 yards of fabric for each the cafeteria. I use 1_ 4 pennant. YOUR MISSION: Eliminate possibilities to find the greatest number of pennants Madison can make with 12 yards of fabric. Is it 6, 9, or 12? Understand Plan Solve You know she has 12 yards of fabric. Each pennant uses 1_ yards of fabric. 1 4 Eliminate the answers that are not reasonable. Madison needs more than 1 yard of fabric for each pennant. So, she needs more than 12 yards for 12 pennants. Eliminate this choice. Now check the choice of 9 pennants. 1 1 1 1 • 1_ + 1_ + 1_ + 1_ = 5. 4 4 4 4 So, Madison can make 4 pennants with 5 yards of fabric. Therefore, she can make 8 pennants out of 10 yards of fabric. • She can also make 1 more pennant with the remaining 2 yards. So, Madison can make 8 + 1 or 9 pennants. Check Making 6 pennants would take 1_ + 1_ + 1_ + 1_ + 1_ + 1_ = 7_ yards. This 4 4 4 4 4 4 2 is not the greatest number she can make. So, making 6 pennants is not reasonable. 1 1 1 1 1 1 1 1. Describe different ways that you can eliminate possibilities when solving problems. 2. Explain how the strategy of eliminating possibilities is useful for taking multiple-choice tests. 3. 248 WR ITING IN MATH Write a problem that could be solved by eliminating possibilities. Chapter 5 Applying Fractions EXTRA PRACTICE See pages 679, 681. Eliminate possibilities to solve Exercises 4–6. 4. TRAINS A train passes through an intersection at the rate of 3 cars per 30 seconds. Assume that it takes 5 minutes for the train to completely pass through the intersection. How many cars does the train have altogether? A 6 cars C 30 cars B 15 cars D 45 cars 8. BRIDGES A covered bridge has a maximum capacity of 48,000 pounds. If an average school bus weighs 10,000 pounds, about how many school buses could a covered bridge hold? 9. GEOMETRY Draw the next two figures in the pattern. 5. PIZZA A pizza shop used 100 pounds of pizza dough to make 125 pizzas. If a large pizza requires 1 pound of dough and a 1 medium pizza requires _ pound, how many 2 large- and medium-sized pizzas were made? 14 hours of sleep each day while a teenager needs about 10 hours of sleep each day. How much more sleep does a 9-month-old need than a teenager? Write as a fraction of a day. F 40 large, 85 medium G 65 large, 60 medium H 55 large, 70 medium J 10. SLEEP A 9-month-old infant needs about 75 large, 50 medium 6. PILLOWS Pat is making pillows out of fabric. 3 He uses _ yard of fabric for each pillow. 4 What is the greatest number of pillows Pat can make with 9 yards of fabric: 9, 12, or 15? Use any strategy to solve Exercises 7–14. Some strategies are shown below. Her ticket costs $7.25, drinks are $3.50, popcorn is $5.75, and pretzels are $4.25. Which two items can Kristen get from the concession stand? 7. MEASUREMENT The diagram shows a shelf 1 inch thick, that holds CDs. Each shelf is _ 8 and the distance between shelves is as shown. How much space is available on each layer of the shelf for a CD? in. 3 average annual precipitation is 50_ inches. 5 1 _ Is inch, 1 inch, or 14 inches the best 49 estimate for the average precipitation per day? 12. MONEY Kristen has $15 to go to the movies. G STRATEGIES PROBLEM-SOLVIN rn. • Look for a patte . rd • Work backwa ized list. • Make an organ in. 11. PRECIPITATION In Olympia, Washington, the 13. PIZZA Sebastian ate _ of a pizza while his 2 5 1 sister ate _ of the same pizza. The remainder 3 was stored in the refrigerator. What fraction of the pizza was stored in the refrigerator? 14. GRADES Jerome had an average of 88 on his first three science tests. His score on the second and third tests were 92 and 87. What was his score on the first test? Lesson 5-4 Problem-Solving Investigation: Eliminate Possibilities 249 Explore 5-5 MAIN IDEA Math Lab Multiplying Fractions Just as the product of 3 × 4 is the number of square units in a rectangle, the product of two fractions can be shown using area models. Use area models to multiply fractions and mixed numbers. _ _ 1 Find 3 × 2 using a geoboard. Math Online 3 4 The first factor is 3 fourths and the second factor is 2 thirds. glencoe.com Use one geoband to show fourths and another to show thirds on the geoboard. • Concepts In Motion Use geobands to form a rectangle. Place one geoband on the peg to show 3 fourths and another on the peg to show 2 thirds. Connect the geobands to show a small rectangle. 1 3 1 3 1 3 2 3 1 4 1 4 1 4 1 4 3 4 The area of the small square is 6 square units. The area of the large 3 6 2 1 rectangle is 12 square units. So, _ ×_ =_ or _ . 3 4 12 2 Find each product using a geoboard. a. _1 × _1 4 b. 3 _1 × _1 2 c. 2 _3 × _1 4 _ 2 Find 2 × 1 using an area model. 4 2 To represent 2 or _, draw 1 2 large rectangles, side by side. Divide each rectangle horizontally into fourths. Color both large rectangles blue. 250 Chapter 5 Applying Fractions 2 d. _2 × _1 3 2 4 Color 1 fourth of each large rectangle yellow. Shading Yellow and blue make green. So, the green sections have been shaded twice and represent the product. 2 1 4 The fraction that compares the number of green sections, 2, to the number of 2 1 or _ . sections in one rectangle, 4, is _ 4 2 4 1 1 =_ . So, 2 × _ 2 Find each product using a model. e. 3 × _ f. 2 × _ 2 3 g. 4 × _ 2 5 h. 3 × _ 3 4 1 2 _ _ 3 Find 1 2 × 1 using a model. 3 2 Draw 2 rectangles divided vertically into thirds and horizontally 2 13 into halves. Color 1_ of the 2 3 squares blue. Color _ of the squares yellow. 2 1 2 13 Then count the small squares that are green. 1 2 3 2 Since the green area is _ of the first rectangle and _ of the second 6 6 3 5 5 2 2 1 rectangle, the total area shaded green is _ +_ or _ . So, 1_ ×_ =_ . 6 6 6 3 2 6 Find each product using a model. i. 1_ × _ 1 4 1 5 j. 2_ × _ 1 2 3 4 k. 1_ × _ 2 3 1 3 ANALYZE THE RESULTS 1. Analyze Exercises a–k. What is the relationship between the numerators of the factors and of the product? between the denominators of the factors and of the product? 2. MAKE A CONJECTURE Write a rule you can use to multiply two fractions. Explore 5-5 Math Lab: Multiplying Fractions 251 5-5 Multiplying Fractions and Mixed Numbers MAIN IDEA Multiply fractions and mixed numbers. Math Online glencoe.com • Extra Examples • Personal Tutor • Self-Check Quiz LUNCH Two thirds of the students at the lunch table ordered a hamburger for lunch. One half of those students ordered cheese on their hamburgers. 1. What fraction of the students at the lunch table ordered a cheeseburger? 2. How are the numerators and 2 1 denominators of _ and _ related 3 2 to the fraction in Exercise 1? Key Concept Multiply Fractions Words To multiply fractions, multiply the numerators and multiply the denominators. Examples Numbers Algebra 1×2 2 _1 × _2 = _ or _ 2 3 2×3 a·c ac _a · _c = _ or _ , where b, d ≠ 0 6 b d b·d bd Multiply Fractions Multiply. Write in simplest form. _ _ 1 1×1 2 3 1×1 _1 × _1 = _ 2 3 2×3 1 _ = 6 2 2× 3 4 3 3 2 2×_ =_ ×_ 4 1 4 2 × 3 =_ 1×4 6 1 =_ or 1_ 2 4 1 2 Multiply the numerators. Multiply the denominators. 1 3 Simplify. _ Whole Numbers When multiplying a fraction by a whole number, write the whole number as a fraction with a denominator of 1. 252 1 shaded green 6 _2 2 Write 2 as . 1 Multiply the numerators. Multiply the denominators. 3 4 Simplify. 6 or 1 1 shaded green 2 4 a. Chapter 5 Applying Fractions _3 × _1 5 2 b. _1 × _3 3 4 c. _2 × 4 3 If the numerator and denominator of either fraction have common factors, you can simplify before multiplying. Simplify Before Multiplying Review Vocabulary GCF the greatest of the common factors of two or more numbers; Example: the GCF of 8 and 12 is 4. (Lesson 4-2) _ _ 3 Find 2 × 3 . Write in simplest form. 7 1 8 _2 × _3 = _2 × _3 7 8 7 Divide 2 and 8 by their GCF, 2. 8 4 1×3 3 =_ or _ 7×4 28 Multiply. Multiply. Write in simplest form. d. _1 × _3 3 e. 7 _4 × _1 9 _5 × _3 f. 8 6 5 Multiply Mixed Numbers _ _ 4 Find 1 × 4 2 . Write in simplest form. 5 2 METHOD 1 2 _2 5 2 5 1 22 _ Rename 4 as an improper fraction, . 5 5 Divide 2 and 22 by their GCF, 2. 22 _1 × 4_2 = _1 × _ 2 _1 × 4 = 2 Rename the mixed number. 11 Simplifying If you forget to simplify before multiplying, you can always simplify the final answer. However, it is usually easier to simplify before multiplying. Estimate 1 × 11 =_ Multiply. 1×5 1 11 =_ or 2_ Simplify. 5 5 METHOD 2 Use mental math. 2 2 is equal to 4 + _ . The mixed number 4 _ 5 ( 5 ) 1 2 1 2 × 4_ =_ 4+_ . Use the Distributive Property to multiply, So, _ 2 5 2 5 then add mentally. ( ) _1 4 + _2 = 2 + _1 2 5 5 1 = 2_ 5 1 2 1 So, _ × 4_ = 2_ . 2 5 5 THINK Half of 4 is 2 and half of 2 fifths is 1 fifth. Rewrite the sum as a mixed number. 1 Check for Reasonableness 2_ ≈ 2 5 ✔ Multiply. Write in simplest form. g. _1 × 8_4 4 9 h. 5_ × 3 1 3 i. 1_ × 2_ 7 8 2 5 Lesson 5-5 Multiplying Fractions and Mixed Numbers 253 Meaning of Multiplication Recall that one meaning of 3 × 4 is three groups with 4 in each group. In Example 5, there are 1 in 365 _41 groups with _ 3 each group. 1 5 SLEEP Humans sleep about _ of each day. If each year is equal to 3 1 365_ days, determine the number of days in a year the average 4 human sleeps. _ 1 1 Humans sleep about _ of 365 days. Words 3 4 Let d represent the number of days a human sleeps. Variable Equation = d 1 1 d=_ · 365_ _1 · 3 365 _ 4 1 Write the equation. 3 4 1,46 1 1 _ _ d= · 3 4 Rename the mixed number as an improper fraction. 487 1,461 1 _ d=_ · 3 Divide 3 and 1,461 by their GCF, 3. 4 1 487 3 d=_ or 121_ 4 4 Multiply. Then rename as a mixed number. 3 The average human sleeps 121_ days each year. 4 4 6 ANIMALS The house cat has an average lifespan that is _ of a lion’s. 5 If a lion’s lifespan is 15 years, find the average lifespan of a house cat. 4 The lifespan of a house cat is _ of that of the lion. Words 5 Let c represent the lifespan of a house cat. Variable Equation 4 c=_ · 15 Real-World Link The average group of lions, called a pride, consists of about 15 2 lions with about of 3 the pride being female. _ Source: African Wildlife Foundation = _ 5 4 c · 15 Write the equation. 5 15 _ c= 4 ·_ 5 1 Write the whole number 15 as an improper fraction. 3 4 _ c=_ · 15 5 1 Divide 5 and 15 by their GCF, 5. 1 12 c=_ or 12 Multiply, then simplify. 1 The average lifespan of a house cat is 12 years. j. COOKING Sofia wishes to make _ of a recipe. If the original recipe 1 2 3 calls for 3_ cups of flour, how many cups should she use? 4 254 Chapter 5 Applying Fractions Examples 1–4 (pp. 252–253) Examples 5, 6 (p. 254) HOMEWORK For Exercises 8–11 12–19 20–23 HELP See Examples 1, 2 3, 4 5, 6 Multiply. Write in simplest form. 1. _2 × _1 2. 2 × _ 4. _1 × _8 5. 2_ × _ 3 2 5 3 1 4 9 4 3. _1 × 4 6 6. 1_ × 3_ 5 6 2 3 3 5 7. WEIGHT The weight of an object on Mars is about _ its weight on 2 5 Earth. How much would an 80-pound dog weigh on Mars? Multiply. Write in simplest form. 3 1 2 2 8. _ × _ 9. _ × _ 8 3 4 5 5 1 1 4 12. _ × _ 13. _ × _ 4 6 9 5 15 7 4 2 16. _ × _ 17. _ × _ 7 8 16 5 10. 1 9×_ 11. 2 1 2 14. _ × _ 4 3 10 3 18. _ × _ 27 8 _4 × 6 5 3 1 15. _ × _ 12 5 5 9 19. _ × _ 6 10 20. DVDs Each DVD storage case is about _ inch thick. What will be the height 1 5 of 12 cases sold together in plastic wrapping? 21. PIZZA Mark left _ of a pizza in the refrigerator. On Friday, he ate _ of what 3 8 1 2 was left of the pizza. What fraction of the entire pizza did he eat on Friday? 22. MEASUREMENT The width of a vegetable garden is _ times its length. If the 3 length of the garden is 7_ feet, what is the width? 1 3 4 23. RECIPES A recipe to make one batch of blueberry muffins calls for 4_ cups 2 3 of flour. How many cups of flour are needed to make 3 batches of blueberry muffins? Multiply. Write in simplest form. 24. 4_ × _ 25. _5 × 2_1 26. 14 × 1_ 27. 3_ × 8 28. 9 × 4_ 29. 4 × 7_ 30. 3_ × 2_ 31. 5_ × 3_ 2 3 4 7 8 2 5 6 2 3 1 7 1 4 2 3 3 4 1 3 3 4 32. MEASUREMENT The width of the fish 2 of its length. What is the width tank is _ 5 of the fish tank? 33. BICYCLING Philip rode his bicycle at 9_ miles 2 5 3 of an hour, how per hour. If he rode for _ 4 many miles did he cover? 30 in. Lesson 5-5 Multiplying Fractions and Mixed Numbers 255 Evaluate each verbal expression. 34. one half of five eighths 35. four sevenths of two thirds 36. nine tenths of one fourth 37. one third of eleven sixteenths MEASUREMENT Find the perimeter and area of each rectangle. 38. 39. 1 3 2 ft 2 1 3 yd 1 6 2 yd 1 5 4 ft 40. POOLS A community swimming pool is 90_ feet long and 55_ feet wide. 2 5 1 2 If Natalie swims the perimeter of the pool four times, what is the total number of feet she will swim? Explain how you solved the problem. MEASUREMENT For Exercises 41–44, use measurement conversions. 41. Find _ of _ of a gallon. 1 1 2 4 1 1 43. Find _ of _ of a kilometer. 100 1,000 42. What is _ of _ of a day? 1 1 60 24 1 1 44. What is _ of _ of a yard? 3 12 _ _ ALGEBRA Evaluate each expression if a = 4, b = 2 1 , and c = 5 3 . 2 45. a × b + c Real-World Link There are an estimated 5 million in-ground swimming pools in the U.S. 46. b × c - a 4 47. 2bc 48. TELEVISION One evening, _ of the students in Rick’s class watched 2 3 3 1 of those students watched a reality show, of which _ television, and _ 8 4 taped the show. What fraction of the students in Rick’s class watched and taped a reality TV show? Source: Pool & Spa Service Industry News 49. FOOD Alano wants to make one and a half recipes of the pasta salad recipe shown at the right. How much of each ingredient will Alano need? Explain how you solved the problem. 50. FIND THE DATA Refer to the Data File on pages 16–19. Choose some data and write a real-world problem in which you would multiply fractions. Pasta Salad Recipe Ingredient broccoli cooked pasta salad dressing cheese Amount _1 4 3 _ 3 c 4 _2 c 3 1 _ 1 c 1 c 3 Write and evaluate a multiplication expression to represent each model. Explain how the models show the multiplication process. 51. EXTRA PRACTICE See pages 680, 708. 256 Chapter 5 Applying Fractions 52. H.O.T. Problems 53. CHALLENGE Two improper fractions are multiplied. Is the product sometimes, always, or never less than 1? Explain your reasoning. 54. OPEN ENDED Write a word problem that involves finding the product 3 1 of _ and _ . 8 4 55. WR ITING IN MATH Refer to Example 2. Explain how the model represents the meaning of the multiplication process. 56. Of the dolls in Marjorie’s doll 57. Which description gives the 1 have red hair. Of these, collection, _ 5 3 _ have green eyes. What fraction of relationship between a term and n, its position in the sequence? 4 Marjorie’s doll collection has both red hair and green eyes? 2 A _ 9 4 C _ 9 3 B _ 19 D _ 20 Position 1 2 3 4 5 Value of Term _1 _1 _3 4 2 4 1 1_ n 1 4 F Subtract 4 from n. 1 G Add _ to n. 20 4 1 . H Multiply n by _ 1 J Divide n by _ . 4 4 58. MEASUREMENT Find which room dimensions would give an area of 3 125_ square feet. Use the eliminate possibilities strategy. 8 (Lesson 5-4) 3 1 A 11_ feet by 10_ feet 2 8 5 C 13_ feet by 9 feet 8 7 1 B 10_ feet by 12_ feet 3 1 D 14_ feet by 8_ feet 8 4 4 2 59. MEASUREMENT How much longer is a 2_ -inch-long piece of string than 2 a_ -inch-long piece of string? 5 1 2 (Lesson 5-3) Replace each ● with <, >, or = to make a true sentence. 60. 5 2 _ ●_ 12 5 61. (Lesson 4-9) 3 1 _ ●_ 16 62. 3_ ● 3_ 7 6 8 6 5 63. PHONES A long-distance telephone company charges a flat monthly fee of $4.95 and $0.06 per minute on all long-distance calls. Write and solve an equation to find the number of monthly minutes spent talking long-distance if the bill total was $22.95. (Lesson 3-5) PREREQUISITE SKILL Solve each equation mentally. 64. x + 2 = 8 65. 9 + m = 12 (Lesson 1-7) 66. 7 - w = 2 Lesson 5-5 Multiplying Fractions and Mixed Numbers 257 5-6 Algebra: Solving Equations MAIN IDEA 1 HOMEWORK Shawnda spends _ hour doing homework after school. Solve equations with rational number solutions. 1 Then she spends another _ hour doing homework before bed. 2 2 1. Write a multiplication expression to find how much time Shawnda spends doing homework. Then find the product. New Vocabulary 2. Copy and complete the table below. multiplicative inverse reciprocal _1 × _3 × _2 = 2 Math Online _5 × _6 = =1 5 3 5 ×_=1 7 _2 × _6 = 2 6 _7 × _8 = 5 6 _7 × = 1 1 8 7 ×8=1 glencoe.com 3. What is true about the numerators and denominators in the • Extra Examples • Personal Tutor • Self-Check Quiz fractions in Exercise 2? Two numbers with a product of 1 are called multiplicative inverses, or reciprocals. Key Concept Inverse Property of Multiplication Words Examples The product of a number and its multiplicative inverse is 1. Numbers Algebra _3 × _4 = 1 4 _a · _b = 1, for a, b ≠ 0 3 b a Find Multiplicative Inverses _ 1 Find the multiplicative inverse of 2 . _2 · _5 = 1 5 2 5 5 2 Multiply _ by _ to get the product 1. 5 2 2 _ 1 The multiplicative inverse of _ is 5 , or 2_ . 5 2 2 1 Find the multiplicative inverse of 2_ . 1 7 2_ =_ 3 3 _7 · 3 = 1 3 7 _ 2 3 Rename the mixed number as an improper fraction. Multiply _7 by _3 to get the product 1. 3 7 1 _ The multiplicative inverse of 2_ is 3 . 3 a. 258 Chapter 5 Applying Fractions _5 6 b. 1_ 1 2 7 c. 8 d. _4 3 In Chapter 3, you learned to solve equations using the Addition, Subtraction, and Division Properties of Equality. You can also solve equations by multiplying each side by the same number. This is called the Multiplication Property of Equality. Key Concept Multiplication Property of Equality Words If you multiply each side of an equation by the same nonzero number, the two sides remain equal. Examples Numbers _x = -3 5=5 Fractions The fraction bar indicates division. So, _2x means x divided by 2. Algebra _2 x = 4 3 _3 · _2 x = _3 · 4 2 5·2=5·2 _x (2) = -3(2) 10 = 10 x = -6 2 2 3 2 x=6 Solve a Division Equation _ 3 Solve 7 = n . Check your solution. 4 n 7=_ 4 n _ 7·4= ·4 4 28 = n Check n 7=_ 4 28 7_ 4 7=7 ✔ Write the equation. Multiply each side of the equation by 4. Simplify. Write the original equation. Replace n with 28. Is this sentence true? _ 4 Solve d = 4.2. 3.5 d _ = 4.2 3.5 Write the equation. d _ · 3.5 = 4.2 · 3.5 3.5 Multiply each side by 3.5. d = 14.7 Simplify. The solution is 14.7. Check d _ = 4.2 Write the original equation. 3.5 14.7 _ 4.2 3.5 Replace d with 14.7. 4.2 = 4.2 ✔ Is this sentence true? Solve each equation. Check your solution. e. 6 = _ m 8 f. p _ = 1.5 2.8 g. k _ = 2.3 4.7 Lesson 5-6 Algebra: Solving Equations 259 Solve a Multiplication Equation _ _ 5 Solve 3 x = 12 . 20 4 12 _3 x = _ 20 4 3 4 _ 12 · x= 4 ·_ 3 3 20 4 (_) Fractions as Coefficients 3 x can The expression _ 4 3 3 be read as _ of x, _4 4 multiplied by x, 3x x divided by 4, or _ 4 multiplied by 3. Write the equation. (_) 1 1 1 4 3 4 3 20 Multiply each side by the reciprocal of _, _. 3 4 4 3 12 _4 · _3 x = _4 · _ 1 1 1 Divide by common factors. 5 4 x=_ Simplify. 5 Solve each equation. Check your solution. h. _1 x = 8 i. 2 _3 x = 9 21 _7 x = _ j. 4 8 64 _ 6 Valerie needs 2 yard of fabric to make each hat for the school play. 3 How many hats can she make with 6 yards of fabric? A 12 C 8 B 9 D 4 Read the Item 2 Each hat needs _ yard of fabric. Given the number of hats, you 3 2 would multiply by _ to find the number of yards of fabric needed. 3 Solve the Item Verify Your Answer It is a good idea to verify your answer by checking the other answer choices. By doing so, you can greatly reduce your chances of making an error. Write and solve a multiplication equation. _2 n = 6 3 3 3 _ · 2n = ·6 2 2 3 (_) (_ ) n=9 Write the equation. _3 Multiply each side by . 2 Simplify. So, the answer is B. k. Wilson has 9 pounds of trail mix. How many _ -pound bags of 260 Chapter 5 Applying Fractions 3 4 trail mix can he make? F 3 H 9 G 6 J 12 Examples 1, 2 (p. 258) Examples 3–5 (p. 259–260) Example 5 (p. 260) Find the multiplicative inverse of each number. 1. _8 2. 5 _2 3. 5_ 4 5 9 4. 9 Solve each equation. Check your solution. 5. k _ =2 8. h 0.5 = _ y 3 6. 4 = _ 16 9. 3.6 7. 12 _3 a = _ 8 b _ = 2.5 8.2 10. 6 = _x 4 7 40 11. FRUIT Three fourths of the fruit in a refrigerator are apples. There are 24 apples in the refrigerator. The number of pieces of fruit is given by the 3 equation _ f = 24. How many pieces of fruit are in the refrigerator? 4 Example 6 (p. 260) HOMEWORK For Exercises 13–20 21–26 33–34 27–32 51–52 HELP See Examples 1, 2 3, 4 5 6 12. MULTIPLE CHOICE Dillon deposited _ of 3 4 his paycheck into the bank. The deposit slip shows how much he deposited. What was the amount of his paycheck? A $15 C $60 B $33.75 D $75 Dillon Gates Find the multiplicative inverse of each number. 13. _5 6 17. 3 14. 11 _ 2 18. 14 15. _1 19. 1 5_ 1 _ 16. 6 10 2 20. 6_ 3 8 Solve each equation. Check your solution. 21. x _ =3 24. w 5=_ 12 4.9 2 12 _ 27. t = _ 5 25 8 2 _ _ 30. = b 3 3 22. 28 = _ d 4 25. h 0.8 = _ 3.6 3 24 _ _ 28. = a 16 4 1 1 _ 31. g = 3_ 2 3 23. b _ =6 26. m _ = 2.8 29. _7 k = _5 32. _3 c = 6_1 2.4 4.6 8 5 6 4 33. DISTANCE The distance d Toya travels in her car while driving d 60 miles per hour for 3.25 hours is given by the equation _ = 60. 3.25 How far did she travel? 34. ANIMALS An adult Fitch ferret weighs about 1.8 kilograms. To find its p weight in pounds p, you can use the equation _ = 2.2. How many pounds 1.8 does an adult Fitch ferret weigh? Lesson 5-6 Algebra: Solving Equations 261 Solve each equation. Check your solution. 35. a _ = 15 36. -8 = _ 38. _5 x = -1.5 39. 37. 34.5 = _m 5 6 r -2 -5 7 _1 t = _3 40. 8 4 _3 m = 1_1 8 2 For Exercises 41–46, define a variable and write an equation. Then solve. 41. CAVES The self-guided Mammoth Cave Discovery Tour includes an 7 elevation change of 140 feet. This is _ of the elevation change on the Wild 15 Cave Tour. What is the elevation change on the Wild Cave Tour? 42. MUSEUMS Twenty-four students brought their permission slips to attend Real-World Link Kentucky’s Mammoth Cave is the longest recorded cave system in the world, with more than 360 miles explored and mapped. The Wild Cave Tour requires visitors to crawl through an opening only 9 inches high. Source: National Park Service 4 the class field trip to the local art museum. If this represented _ of the class, 5 how many students are in the class? 43. MEASUREMENT If one serving of cooked rice is _ cup, how many servings 3 4 1 will 16_ cups of rice yield? 2 44. HIKING After Alana hiked 2_ miles along a hiking trail, she realized that 5 8 3 she was only _ of the way to the end of the trail. How long is the trail? 4 45. SLEEP The average person spends _ of his life asleep. According to this, if a 1 3 person has spent 26 years asleep, how old is he? 46. ANALYZE TABLES Tierra recorded the EXTRA PRACTICE See pages 681, 708. H.O.T. Problems Distance Ran in One Week distance she ran each day last week. 5 If she ran _ of her weekly running goal, 6 what was her running goal? Day 47. REASONING Complete the statement: If 8 = _, then m - 12 = . Explain your reasoning. m 4 Distance (mi) Monday 1 Wednesday 2 _3 4 _1 2 1 _ 2 Friday 1 Saturday 4 48. Which One Doesn’t Belong? Identify the pair of numbers that does not belong with the other three. Explain. 6 9 _ _ , 6 9 1 4, _ 4 _3 , 5 _2 , _7 5 7 2 49. CHALLENGE The formula for the area of a b1 1 trapezoid is A = _ h(b1 + b2), where b1 and b2 2 are both bases and h is the height. Find the value of h in terms of A, b1, and b2. Justify your answer. h b2 50. WR ITING IN MATH Explain the Multiplication Property of Equality. Then give an example of an equation in which you would use this property to solve the equation. 262 Chapter 5 Applying Fractions 51. Audrey drove 200 miles in 3.5 hours. 52. The table shows the results of a survey. Which equation can you use to find the rate r at which Audrey was traveling? Music Preference Type Fraction of Students pop _5 B 200 · 3.5 = r jazz _1 r C _ = 200 rap _1 A 200 = 3.5r 8 8 4 3.5 D 200r = 3.5 If there are 420 students surveyed, which equation can be used to find the number of students s who prefer rap? 1 F _ s = 420 1 H s+_ = 420 4 4 1 1 · 420 J 420 + s = _ G s=_ 4 4 Multiply. Write in simplest form. 3 4 53. _ × _ 8 9 (Lesson 5-5) 1 54. 1_ × 6 2 55. 2_ × _ 2 5 56. 1_ × 1_ 1 6 1 2 7 9 57. COOKING Lawana had 4_ cups of chopped walnuts. She used 1_ cups in 2 3 1 4 a recipe. How many cups of chopped walnuts are left? Write each percent as a decimal. 58. 25% (Lesson 5-3) (Lesson 4-7) 59. 8% 60. 25.6% 61. 123% 62. MEASUREMENT A farmer has a rectangular pumpkin field with a perimeter of 3,800 feet. If the width of the pumpkin field is 800 feet, what is the length of the field? (Lesson 3-6) ALGEBRA Solve each equation. Check your solution. 63. 7 = x + 8 64. k - 3 = -14 66. ALGEBRA The table below shows the time needed to complete 4 art projects. If the pattern continues, how much time is needed to complete the fifth art project? (Lesson 2-7) PREREQUISITE SKILL Estimate. 67. 18_ ÷ 3 1 6 (Lesson 3-2) Project 1 2 3 4 Time (min) 8 25 42 59 70. 9 6 _ ÷_ 5 (Lesson 5-1) 68. 24_ ÷ 11_ 3 8 65. -2 = m + 6 7 9 69. 2 11 _ ÷_ 11 12 10 7 Lesson 5-6 Algebra: Solving Equations 263 Meaning of Division You know that one meaning of division is to put objects into equal groups. But there are other meanings too. Look for these meanings when you’re solving a word problem. To share Zach and his friend are going to share 3 apples equally. How many apples will each boy have? To take away equal amounts Isabel is making bookmarks from a piece of ribbon. Each bookmark is 6.5 centimeters long. How many bookmarks can she make from a piece of ribbon that is 27 centimeters long? 26 cm 6.5 cm 6.5 cm 6.5 cm 6.5 cm To find how many times greater The Nile River, the longest river on Earth, is 4,160 miles long. The Rio Grande River is 1,900 miles long. About how many times longer is the Nile than the Rio Grande? Nile River 4,160 mi Rio Grande 1,900 mi Rio Grande 1,900 mi 1. Solve each problem above. Identify the meaning of division shown in each problem. Then solve the problem. 2. A landscape architect wants to make a border along one side of a garden using bricks that are 0.25 meter long. If the garden is 11.25 meters long, how many bricks does she need? 3. The Jackson family wants to buy a flat-screen television that costs $1,200. They plan to pay in six equal payments. What will be the amount of each payment? 4. A full-grown blue whale can weigh 150 tons. An adult African elephant weighs about 5 tons. How many times greater does a blue whale weigh than an African elephant? 5. Each story in an office building is about 4 meters tall. The Eiffel Tower in Paris, France, is 300 meters tall. How many stories tall is the Eiffel Tower? 264 Chapter 5 Applying Fractions 5-7 Dividing Fractions and Mixed Numbers MAIN IDEA Cut two paper plates into four equal pieces each to show 2 ÷ 1 . _ Divide fractions and mixed numbers. 4 1. Math Online 4 2. How would you model 3 ÷ _? glencoe.com • Concepts In Motion • Extra Examples • Personal Tutor • Self-Check Quiz 1 4 1 4 1 How many _ ’s are in 2 plates? 1 2 1 4 1 4 1 4 1 4 1 4 1 4 3. What is true about 3 ÷ _ and 3 × 2? 1 2 1 Dividing 8 by 2 gives the same result as multiplying 8 by _ , which 2 1 is the same as is the reciprocal of 2. In the same way, dividing 4 by _ 3 1 , or 3. multiplying 4 by the reciprocal of _ 3 reciprocals _ 8· 1 =4 2 8÷2=4 _ reciprocals 4 ÷ 1 = 12 3 same result 4 · 3 = 12 same result Is this pattern true for any division expression? _7 3 8 7 Consider _ ÷_ , which can be rewritten as _ . 8 _7 _7 × _4 _3 _3 × _4 _3 4 4 Multiply the numerator and denominator 3 4 by the reciprocal of , which is . 3 8 _8 = _ 4 _ _ 4 3 4 _7 × _4 3 _3 × _4 = 1 8 3 =_ 4 1 3 7 4 =_ ×_ 8 3 3 7 7 4 ÷_ =_ ×_ . These examples suggest the following rule. So, _ 8 4 8 3 Key Concept Divide by Fractions Words Examples To divide by a fraction, multiply by its multiplicative inverse, or reciprocal. Numbers _7 ÷ _3 = _7 · _4 8 4 8 3 Algebra _a ÷ _c = _a · _d , where b, c, d ≠ 0 b d b c Lesson 5-7 Dividing Fractions and Mixed Numbers 265 Divide by a Fraction _ _ 1 Find 3 ÷ 1 . Write in simplest form. 2 4 Estimate 1 ÷ _1 = 2 Think: How many groups of _3 ÷ _1 = _3 · _2 2 4 2 2 _1 _2 Multiply by the reciprocal of , which is . 2 1 4 _1 are in 1? 1 ÷ _1 = 2 1 1 3 _ =_ ·2 4 Divide 4 and 2 by their GCF, 2. 1 2 3 1 =_ or 1_ 2 Multiply. 2 1 1_ ≈2 ✔ Check for Reasonableness 2 Divide. Write in simplest form. a. _3 ÷ _1 4 b. 4 _4 ÷ _8 5 c. 9 _5 ÷ _2 6 3 To divide by a mixed number, first rename the mixed number as an improper fraction. Then multiply the first fraction by the reciprocal, or multiplicative inverse, of the second fraction. Divide by Mixed Numbers _ _ 2 Find 2 ÷ 3 1 . Write in simplest form. 3 Estimate 3 _1 ÷ 3 = _1 × _1 or _1 2 2 10 _2 ÷ 3_1 = _2 ÷ _ 3 3 3 3 3 2 =_·_ 3 10 1 1 3 10 2 _ =_ · 3 1 1 =_ 5 3 3 266 _1 Rename 3 as an improper fraction. 3 Multiply by the reciprocal of 10 3 _ , which is _. 3 10 Divide out common factors. 5 Multiply. Check for Reasonableness Dividing by a Whole Number Remember that a whole number can be written as a fraction with a 1 in the denominator. 1 So, 2 _ ÷ 5 can be 3 5 1 rewritten as 2 _ ÷ _. 6 _1 is close to _1 . ✔ 5 6 Divide. Write in simplest form. d. 5 ÷ 1_ 1 3 e. - _ ÷ 1_ 3 4 1 2 f. 2_ ÷ 5 1 3 g. NUTS In planning for a party, 5_ pounds of cashews will 1 Chapter 5 Applying Fractions 1 4 3 be divided into _ -pound bags. How many such bags can 4 be made? 3 WOODWORKING Students in a woodworking class are making butterfly houses. The side pieces of the house need to be 8 1 inches long. 4 How many side pieces can be cut from _ _ 1 a board measuring 49 1 inches long? 8 4 in. 2 To find how many side pieces can be cut, 1 1 by 8_ . divide 49_ 2 4 48 ÷ 8 = 6 Estimate Use compatible numbers. 99 33 1 1 49_ ÷ 8_ =_ ÷_ 2 4 Rename the mixed numbers as improper fractions. 2 4 99 4 =_·_ 2 33 3 2 2 33 Multiply by the reciprocal of 99 _ =_ · 4 1 33 4 _ , which is _. 4 33 Divide out common factors. 1 6 =_ or 6 Multiply. 1 So, 6 side pieces can be cut. Check for Reasonableness The answer matches the estimate. ✔ h. FOOD Suppose a small box of cereal contains 12_ cups of cereal. 1 -cup servings are in the box? How many 1_ 2 3 3 i. MEASUREMENT The area of a rectangular bedroom is 146_ square 7 8 3 feet. If the width of the bedroom is 11_ feet, find the length. 4 Examples 1–3 (pp. 266–267) Divide. Write in simplest form. 1. _1 ÷ _1 8 3 1 1 _ 5. ÷ 7_ 2 2 Example 2 (p. 266) Example 3 (p. 267) 2. _3 ÷ _1 5 4 4 2 _ 6. ÷ 1_ 7 7 3. 3 ÷ _ 6 7 7. 4. 3 2 5_ ÷ 4_ 5 3 _3 ÷ 6 4 8. 6_ ÷ 3_ 1 2 5 7 9. FOOD Deandre has 7 apples, and each apple is divided evenly into eighths. How many apple slices does Deandre have? 10. WALKING On Saturday, Lindsay walked 3_ miles 2 hours. What was her walking pace, in 1_ 1 2 5 in miles per hour? Lesson 5-7 Dividing Fractions and Mixed Numbers 267 HOMEWORK For Exercises 11–14 15–32 HELP See Examples 1 2, 3 Divide. Write in simplest form. 11. _3 ÷ _6 12. 8 7 1 15. 6 ÷ _ 2 _5 ÷ _5 13. 9 6 4 16. _ ÷ 2 9 _2 ÷ _1 3 _7 ÷ _3 14. 2 8 4 1 18. 5 ÷ 1_ 3 17. 2_ ÷ 4 2 3 19. FOOD Mason has 8 cups of popcorn kernels to divide into _ -cup portions. 2 3 How many portions will there be? 20. MOVIES Cheryl is organizing her movie collection. If each movie case is _3 inch wide, how many movies can fit on a shelf 5 feet wide? 4 Divide. Write in simplest form. 21. _2 ÷ 2_1 3 2 25. 3_ ÷ 1_ 4 5 1 3 22. _8 ÷ 5_1 9 3 26. 9_ ÷ 2_ 5 6 1 2 23. 4_ ÷ 6_ 24. 5_ ÷ 2_ 3 1 2 4 1 2 _ _ 27. 5 ÷ 5 3 2 1 7 7 3 7 _ _ 28. 6 ÷ 8 4 29. ICE CREAM Vinh bought 4_ gallons of ice cream to serve at his birthday 1 2 1 of a gallon, how many pint-sized servings can be made? party. If a pint is _ 8 30. BEVERAGES William has 8_ cups of fruit juice. If he divides the juice 1 4 3 -cup servings, how many servings will he have? into _ 4 BIRDS For Exercises 31 and 32, use the table that gives information about several types of birds of prey found at the Woodland Park Zoo in Seattle, Washington. 31. How many times as heavy is the Golden Eagle as the Red-tailed Hawk? 32. How many times as heavy is the Golden Eagle as the Northern Bald Eagle? Bird Golden Eagle Northern Bald Eagle Red-Tailed Hawk Maximum Weight (lb) _9 10 9 _ 9 10 1 3_ 13 2 Source: Woodland Park Zoo Draw a model of each verbal expression and then evaluate the expression. Explain how the model shows the division process. Real-World Link Red-tailed hawks are large, stocky birds with long, broad wings and short, broad tails. Females are larger than males and can weigh up to 1 3_ pounds. 2 Source: Woodland Park Zoo 268 33. one half divided by two fifths 34. five eighths divided by one fourth 35. one and three eighths divided by one half 36. two and one sixth divided by two thirds 37. PIZZA A concession stand sells three types of pizza. The diagram shows how much pizza of each type is left after the concession stand was open for one hour. If the pizza is sold in 1 slices that are _ of a whole pizza, 8 how many more slices can be sold? Chapter 5 Applying Fractions Sausage Cheese Supreme _ _ _ ALGEBRA Evaluate each expression if g = 1 , h = 1 , and j = 3 2 . 38. j ÷ h 6 39. g ÷ j 2 3 40. 3g ÷ h 41. h ÷ (_12 j) 42. SHOPPING A supermarket sells pretzels in _ -ounce snack-sized bags or 3 4 1 -ounce regular-sized bags. How many times larger is the regular-sized 12_ 2 bag than the snack-sized bag? 43. MEASUREMENT A recipe calls for 2_ cups of brown sugar and _ cup of 2 3 2 3 confectioner’s sugar. How many times greater is the number of cups of brown sugar in the recipe than of confectioner’s sugar? SCHOOL For Exercises 44 and 45, use the table that shows the number of hours students spend studying each week during the school year. Weekly Study Hours Fraction of Students Hours _1 50 _2 25 11 _ 50 17 _ 100 _1 5 _1 5 _3 none 44. How many times greater was the 1–2 number of students who spent over 10 hours each week studying than those who spent only 1–2 hours each week studying? 3–5 6–7 8–10 45. How many times greater was the number of students who spent 3 or more hours each week studying than those who spent less than 3 hours each week studying? Over 10 Not sure 25 Source: Time Magazine 46. SCHOOL SUPPLIES Tara bought a dozen folders. She took _ of the dozen 1 3 and then divided the remaining folders equally among her four friends. What fraction of the dozen did each of her four friends receive and how many folders was this per person? 47. WEATHER A meteorologist has issued a thunderstorm warning. So far, the EXTRA PRACTICE See pages 681, 708. H.O.T. Problems 1 storm has traveled 35 miles in _ hour. If it is currently 5:00 p.m., and the 2 storm is 105 miles away from you, at what time will the storm reach you? Explain how you solved the problem. 48. CHALLENGE If _ is divided by a certain fraction _, the result is _. What is 5 6 a b the fraction _a ? 1 4 b 49. SELECT A TOOL Reynaldo cut a rope to make the running knot shown. The rope used to 3 1 feet long and was _ of make the knot was 1_ 2 4 the original rope length. Which of the following tools could be used to determine the rope’s original length? Justify your selection(s). Then use your tool(s) to find the length. paper and pencil model calculator real object Lesson 5-7 Dividing Fractions and Mixed Numbers 269 50. FIND THE ERROR Evan and José are finding _ ÷ _. Who is correct? Explain 4 5 your reasoning. _4 ÷ _6 = _4 · _7 5 5 6 7 14 _ = 28 or _ _4 ÷ _6 = _5 · _6 5 7 6 7 4 7 30 1 _ = 28 or 1_ 14 15 30 Evan 51. José WR ITING IN MATH If you divide a proper fraction by another proper fraction, is it possible to get a mixed number as an answer? Explain your reasoning. 53. How many 1_ -pound boxes of 1 8 52. The Corbett family owns 300 acres of 3 pounds peanuts can be made using 6_ 4 of peanuts? land that they plan to rent to people 1 for their horses. How many 7_ -acre 2 lots can they make using the 300 acres? F 4 H 6 1 C 40_ 2 1 D 292_ 2 G 5 J A 21 B 40 Find the multiplicative inverse of each number. 6 54. _ 7 4 55. _ 13 7 (Lesson 5-6) 57. 5_ 1 4 56. 8 58. Find _ × _. Write in simplest form. (Lesson 5-5) 1 10 5 8 59. MEASUREMENT Find the length of a rectangular flower bed if the perimeter is 12 feet and the width is 1.5 feet. (Lesson 3-6) 60. ANIMALS An elephant herd can move 50 miles in a day. At this rate, about how many miles can an elephant herd move each hour? (Lesson 1-1) in Geography A Traveling We Will Go It’s time to complete your project. Use the data you have gathered about schedules and costs to prepare a travel brochure for your vacation destination. Be sure to include a paragraph describing why you chose your vacation spot. Unit Project at glencoe.com g 270 Chapter 5 Applying Fractions 5 Math Online Study Guide and Review glencoe.com • • Vocabulary Review Key Vocabulary compatible numbers Be sure the following Big Ideas are noted in your Foldable. multiplicative inverse (p. 258) (p. 232) reciprocal (p. 258) like fractions (p. 236) Fractions Estimating with Fractions unlike fractions (p. 237) Mix Numbeed rs (Lesson 5-1) • When the numerator is much smaller than the denominator, round the fraction to 0. • When the numerator is about half of the 1 denominator, round the fraction to _. 2 • When the numerator is almost as large as the denominator, round the fraction to 1. Adding and Subtracting Fractions (Lessons 5-2 and 5-3) Vocabulary Check Choose the correct term or number to complete each sentence. 1. To add like fractions, add the (numerators, denominators). 2. The symbol ≈ means (approximately, exactly) equal to. • To add or subtract like fractions, add or subtract the numerators and write the result over the denominator. 3. When dividing by a fraction, multiply by • To add or subtract unlike fractions, rename the fractions using the LCD. Then add or subtract as with like fractions. a fraction is much smaller than the 1 denominator, round the fraction to 0, _ . • To add or subtract mixed numbers, first add or subtract the fractions. If necessary, rename them using the LCD. Then add or subtract the whole numbers and simplify if necessary. Multiplying and Dividing Fractions (Lessons 5-5 and 5-7) • To multiply fractions, multiply the numerators and multiply the denominators. • The product of a number and its multiplicative inverse is 1. • To divide by a fraction, multiply by its multiplicative inverse, or reciprocal. its (value, reciprocal). 4. When estimating, if the numerator of 2 5. Fractions with different denominators are called (like, unlike) fractions. 6. The multiplicative inverse of _ is 5 6 (_65 , -_56 ). 7. The mixed number 2 _ can be renamed ( 4 7 ) 7 _ as 2 _ , 1 11 . 7 7 8. When multiplying fractions, multiply the numerators and (multiply, keep) the denominators. 9. The reciprocal of _ is (-3, 3). 1 3 10. The fractions _ and _ are (like, unlike) fractions. 4 16 2 4 11. Another word for multiplicative inverse is (reciprocal, denominator). Solving Equations (Lesson 5-6) If you multiply each side of an equation by the same nonzero number, the two sides remain equal. 12. The fraction _ can be read x multiplied by ( ) 1 2, _ . 2 x 2 Chapter 5 Study Guide and Review 271 5 Study Guide and Review Lesson-by-Lesson Review 5-1 Estimating with Fractions (pp. 230–235) Example 1 Estimate. 13. 2_ ÷ 1_ 14. 6_ - 5_ 9 1 8 10 13 1 _ _ 15. × 5 15 1 17. _ · 25 2 2 9 16. _1 + _3 1 7 _ 12 5 5 is almost as large as 6, so 2_ ≈ 3. 2 8 6 1 18. 15_ ÷ 7_ 7 3 6 12 5 18_ feet and the width of her living 8 1 feet. About how many room is 9_ 2 square feet of carpet would be needed for her living room? 20. FOOTBALL Jamil practiced football for 3 2 1_ hours on Saturday and 2_ hours on 3 4 Sunday. About how many more hours did he practice on Sunday than on Saturday? The sum is about 8. 21. 22. 6 6 1 _ _ 23. +5 9 9 5 _ _ 25. - 5 8 12 Example 2 9 _3 + _ 7 ≈ 1. 7 is almost as large as 8, so _ 8 4 1 ≈_ . 4 is about half of 7, so _ 8 7 2 2 2 Example 3 _ _ Find 1 + 2 . 6 3 _1 6 2 +_ 3 ____ _5 6 4 How much rain fell between 8 a.m. and 4 p.m.? 28. PIZZA Owen ate _ of a pizza Tuesday night. The next day, he ate an 1 of the pizza. What fraction additional _ 2 of the pizza has he eaten? Chapter 5 Applying Fractions 2 1 The difference is about _ . _1 inch. By 4 p.m., the gauge read _3 inch. 272 7 _7 - _4 ≈ 1 - _1 or _1 27. RAIN At 8 a.m., Della’s rain gauge read 1 8 7 8 Use a model. 7 14 9 3 _ 24. -_ 10 10 3 7 26. _ + _ 20 4 8 _ _ Estimate 7 - 4 . (pp. 236–241) Add or subtract. Write in simplest form. _2 - _1 6 5 1 5_ + 2_ ≈ 5 + 3 or 8 her living room. It has a length of Adding and Subtracting Fractions 6 12 1 ≈ 5. 1 is much smaller than 12, so 5_ 19. MEASUREMENT Gina wishes to carpet 5-2 _ Estimate 5 1 + 2 5 . Example 4 _ _ Find 3 - 1 . 10 3 6 5 1 _ -_ =_ -_ 10 4 20 1 =_ 20 20 4 Rename the fractions using the LCD, 20. Subtract the numerators. Mixed Problem Solving For mixed problem-solving practice, see page 708. 5-3 Adding and Subtracting Mixed Numbers (pp. 242–246) Example 5 29. 3_ + 6_ 3 2 1 4 + 3_ = 5_ + 3_ 5_ 30. 4_ - 2_ 9 2 15 15 6 2 31. 8_ + 1_ 7 7 3 1 _ _ 33. 7 - 5 5 3 5 1 _ 35. 3 + 11_ 8 2 1 2 3 3 3 11 _ 32. 7 - 4_ 12 12 3 1 34. 5_ + 1_ 6 4 3 4 _ 36. 4 - 2_ 5 10 37. BABYSITTING Lucas watched his little 1 2 sister for 2_ hours on Friday, 3_ hours 2 3 3 hours on Sunday. on Saturday, and 1_ 3 6 6 6 Add the whole numbers and add the fractions. 1 = 9_ 8 = 8 + 1 or 9 _7 5 _1 6 _ 6 5 3 _ =1 5 5 _1 6 _ Find 4 1 - 2 3 . 3 6 3 1 - 2_ = 3_ - 2_ 4_ 5 2 Rename the fractions. 7 = 8_ Example 6 4 PSI: Eliminate Possibilities 2 _ 3 6 How many hours did Lucas watch his little sister? 5-4 _ Find 5 2 + 3 1 . Add or subtract. Write in simplest form. 5 5 _1 _6 Rename 4 as 3 . 5 5 Subtract the whole numbers and subtract the fractions. (pp. 248–249) Solve by eliminating possibilities. 38. SCHOOL It takes Beth 15 minutes to Example 7 A group of friends went to a theme park. Six of the friends rode the _ 1 walk to school, _ mile away. What is 2 her walking pace? Ferris wheel. If this was 2 of the group, 3 how many friends were in the group? A 2 miles per hour A 3 B 1 mile per hour B 6 C 7.5 miles per hour C 9 D 30 miles per hour D 12 39. COOKING Which of the following would yield a larger batch of bagels? 1 F Multiply a recipe by _ . 1 . G Divide a recipe by _ 2 2 3 . H Multiply a recipe by _ 4 J Divide a recipe by 3. Since 6 friends rode the Ferris wheel 2 and this was _ of the total number of 3 friends in the group, the number of friends in the group must be greater than 6. So, eliminate choices A and B. If there were 12 friends in the group, the 6 that rode the Ferris wheel would 1 represent _ of the group. So, eliminate 2 choice D. Choice C is the only remaining possibility. 6 2 Since 6 out of 9 is _ or _ , C is correct. 9 3 Chapter 5 Study Guide and Review 273 5 Study Guide and Review 5-5 Multiplying Fractions and Mixed Numbers (pp. 252–257) 40. _3 × _2 41. 42. 10 _3 × _ 43. 4 × _ 44. 3 1 2_ ×_ 45. 4_ × 2_ 5 7 5 21 3 5 4 _ ×_ 12 1 2 4 9 13 20 _ _ Find 5 × 2 . Example 8 Multiply. Write in simplest form. 9 5×2 _5 × _2 = _ 9 9×3 3 10 =_ 1 12 Simplify. 27 _ _ Find 3 1 × 2 3 . Example 9 46. FOOD An average slice of American 1 inch thick. What is cheese is about _ 8 the height of a package containing 20 slices? 2 3 1 7 11 × 2_ =_ ×_ 3_ 2 2 4 3 Multiply the numerators and multiply the denominators. 4 _1 _3 Rename 3 and 2 . 4 2 4 Multiply the numerators and multiply the denominators. 7 × 11 =_ 2×4 5 77 =_ or 9_ Simplify. 8 5-6 Algebra: Solving Equations (pp. 258–263) Example 10 Find the multiplicative inverse of 9 . Find the multiplicative inverse of each number. 47. 7 _ _ 49. 3_ 1 3 48. 5 12 _9 · _5 = 1 5 The product of 9 _9 and _5 is 1. 5 9 Solve each equation. Check your solution. 50. 8 = _ Example 11 52. n -7.6 = _ 3 51. _4 b = 12 53. x _ = 2.5 5 _4 · _3 g = _4 · 2 3 4 mysteries. If there are 10 mystery books, how many books are on the shelf? Dividing Fractions and Mixed Numbers Divide. Write in simplest form. _3 ÷ _6 5 7 57. 2_ ÷ _ 3 5 6 4 3 1 _ 59. 4 ÷ 2_ 5 10 56. 4 ÷ _ 2 3 58. -_ ÷ 3 2 5 8 2 _ 60. - ÷ _ 21 7 1 61. MEASUREMENT How many _ -inch 8 3 _ lengths are in 6 inches? 4 Chapter 5 Applying Fractions 4 Write the equation. Multiply each side by 4 0.3 2 3 55. _ Solve 3 g = 2. _3 g = 2 54. BOOKS Of the books on a shelf, _ are 274 5 9 _ The multiplicative inverse of _ is 5 . 5 9 w 2 5-7 8 _3 the reciprocal of . 3 8 2 g=_ or 2_ 3 3 4 Simplify. (pp. 265–270) Example 12 _ _ Find 2 4 ÷ 7 . 4 7 14 7 ÷_ =_ ÷_ 2_ 5 10 5 10 5 10 _4 Rename 2 . 5 2 2 Multiply by the 5 7 reciprocal of 14 _ =_ · 10 1 1 4 =_ or 4 1 Simplify. _7 . 10 5 Practice Test 1. 7 2 5_ - 1_ 3. 13 _3 × _ 9 • Chapter Test 13 15 2. 5 1 3_ + 6_ received a check from his grandmother. Of this amount, the table shows how he spent or saved the money. 7 12 2 4 4. 5_ ÷ 1_ 3 5 Fraction of Check 5. BAKING A restaurant uses 2_ pounds of 3 4 8. 10. 12. 14. 8 4 _ +_ 15 15 _5 × _2 8 5 5 1 _ 4 - 2_ 12 12 5 4 8_ - 1_ 7 14 _8 ÷ 5_1 9 3 7. 9. 11. 13. 15. _1 spent on a CD 7 _ 20 deposited into savings account 2 Two weeks later, he withdrew _ of the 7 1 _ -_ 3 6 8 _ 6× 21 5 7 _ 6 + 3_ 9 12 5 2 4_ × 1_ 6 3 _1 ÷ 5 6 10 amount he had deposited into his savings account. What fraction of the original check did he withdraw from his savings account? 2 F _ 7 H _ 3 9 G _ 23 16. MULTIPLE CHOICE Seth drove 5_ miles to the 3 4 1 16 3 pounds? How many ounces are in 8_ 4 6 miles to the park. What is the total distance Seth drove? J 30 7 _ 40 20. MEASUREMENT An ounce is _ of a pound. 5 1 bank, 6_ miles to the post office, and 4_ 3 spent on baseball cards 4 Add, subtract, multiply, or divide. Write in simplest form. How Spent or Saved 5 _2 flour to make a batch of dinner rolls. About how many pounds of flour are needed if 3 batches of dinner rolls are to be made? 6. glencoe.com 19. MULTIPLE CHOICE For his birthday, Keith Estimate. 7 Math Online 9 A 15_ miles ALGEBRA Solve each equation. Check your solution. 7 miles B _ 12 21. 13 11 miles C _ 12 y _ = 8.1 3.7 3 5 _ 23. =_ x 8 4 22. 6 = _m 2 5 24. 3_ = _p 1 6 2 3 11 miles D 16_ 12 17. SPORTS Tyler’s football practice lasted 1 1 hours. If _ of the time was spent catching 2_ 2 4 passes, how many hours were spent catching passes? 18. MEASUREMENT The floor of a moving van 5 1 feet long and 7_ feet wide. Find is 11_ 3 12 the area of the moving van floor. 25. MULTIPLE CHOICE Maria is making a mural 2 that is 9_ feet long. She wants to divide the 3 5 mural into sections that are each _ foot. 8 Which equation can be used to find n, the number of sections in Maria’s mural? 5 2 A _ n = 9_ 8 3 2 _ _ B 9 n= 5 3 8 5 2 C _ + n = 9_ 8 3 5 2 D n-_ = 9_ 8 3 Chapter 5 Practice Test 275 5 Math Online Test Practice Cumulative, Chapters 1–5 glencoe.com • Test Practice 4. The fraction _ is found between which pair 5 6 of fractions on a number line? Read each question. Then fill in the correct answer on the answer sheet provided by your teacher or on a sheet of paper. 1. Mrs. Brown needs to make two different desserts for a dinner party. The first recipe 1 requires 2_ cups of flour, and the second 4 3 cup less than the first. recipe requires _ 4 Which equation can be used to find n, the number of cups of flour needed for the second recipe? 3 1 -_ A n = 2_ 4 4 1 _ B n = 2_ ·3 4 4 3 1 C n = 2_ +_ 4 4 3 1 D n = 2_ ÷_ 4 4 5 1 F _ and _ 8 4 1 4 G _ and _ 3 9 31 11 H _ and _ 36 12 7 17 and _ J _ 12 18 5. The table shows the distance Kelly swam over a four-day period. What was the total distance, in miles, Kelly swam? Kelly’s Swimming Day Distance (miles) 2. Which of the following is true concerning the least common multiple of 6 and 9? Monday 1.5 F It is greater than the least common multiple of 8 and 12. Tuesday 2 G It is greater than the least common multiple of 5 and 15. Wednesday 2.3 Thursday 3 H It is less than the least common multiple of 4 and 6. J It is less than the least common multiple of 3 and 4. _3 4 _1 2 A 10.5 miles 1 C 10_ miles 1 miles B 10_ 4 D 9 miles 20 3. Kyle’s hockey team has 6 sixth graders, 9 seventh graders, and 5 eighth graders. Which statement below is true? 6. Which of the following gives the correct 5 1 meaning of the expression _ ÷_ ? 8 A One fourth of the team members are sixth graders. 5 8 3 1 F _ ÷_ =_ ×_ 8 3 5 1 B More than half of the team members are seventh graders. 5 5 3 1 G _ ÷_ =_ ×_ C 25% of the team members are eighth graders. 5+1 5 1 H _ ÷_ =_ D 30% of the team members are seventh graders. 5 5 1 1 J _ ÷_ =_ ×_ 276 Chapter 5 Applying Fractions 8 8 8 3 3 3 8 1 8+3 8 3 3 Preparing for Standardized Tests For test-taking strategies and practice, see pages 716–733. 7. What is the value of the expression (3 + 4)2 ÷ 7 - 2 × 6? A -9 C 30 B -5 D 1 Record your answers on the answer sheet provided by your teacher or on a sheet of paper. 10. Write an equation using two variables to 8. Which line contains the ordered show the relationship between the position x and the value of a term y. pair (-1, 2)? y k O l x Position (x) 1 2 3 4 5 Value of Term (y) 5 9 13 17 21 n n 11. Evan runs 2_ miles each week. He runs 3 8 m _3 mile on Mondays and _3 mile on Tuesdays. 4 F Line k 4 How far does he run, in miles, if the only other day he runs each week is Thursday? G Line l H Line m 12. Find 15 ÷ (-5). J Line n 9. A pizza shop tried 45 new types of pizza during the past year and 20% of them became popular. Which best represents the fraction of pizzas that did not become popular? Record your answers on the answer sheet provided by your teacher or on a sheet of paper. Show your work. 1 A _ 13. A box of laundry detergent contains 35 cups. 3 C _ 5 _ B 4 9 5 1 It takes 1_ cups per load of laundry. 4 D _ 5 4 a. Write an equation to represent how many loads you can wash with one box. b. How many loads can you wash with Question 9 Be sure to pay attention to emphasized words, or words that are italicized. In Question 9, you are asked to find which answer is not correct. one box? c. How many loads can you wash with 3 boxes? NEED EXTRA HELP? If You Missed Question... 1 2 3 4 5 6 7 8 9 10 11 12 13 Go to Lesson... 5-2 4-8 4-6 4-9 4-5 5-7 1-4 3-7 4-6 1-10 5-2 2-8 5-7 Chapters 1–5 Test Practice 277
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