Objective 1 To introduce multiplication with mixed numbers. materials Teaching the Lesson Key Activities Students review conversions from mixed numbers to fractions and from fractions to mixed numbers. Then they multiply mixed numbers by applying the conversions and by using the partial-products method. Key Concepts and Skills • Convert between fractions and mixed numbers. [Number and Numeration Goal 5] • Multiply mixed numbers. [Operations and Computation Goal 5] • Use the partial-products algorithm to multiply whole numbers, fractions, and mixed numbers. Щ— Math Journal 2, pp. 272–274 Щ— Study Link 8 7 бњ Щ— Teaching Aid Master (Math Masters, 414; optional) Щ— slates See Advance Preparation [Operations and Computation Goal 5] Ongoing Assessment: Informing Instruction See page 661. Ongoing Assessment: Recognizing Student Achievement Use journal page 273. [Operations and Computation Goal 5] 2 Ongoing Learning & Practice Students practice using unit fractions to find a fraction of a number. Students practice and maintain skills through Math Boxes and Study Link activities. 3 materials Щ— Math Journal 2, pp. 275 and 276 Щ— Study Link Master (Math Masters, p. 237) materials Differentiation Options READINESS EXTRA PRACTICE Students compare and order improper fractions. Students practice converting between fractions, decimals, and percents by playing Frac-Tac-Toe. Additional Information Advance Preparation For Part 1, draw several blank “What’s My Rule?” rule boxes and tables on the board to use with the Study Link 8 7 Follow-up. бњ Щ— Student Reference Book, pp. 309–311 Щ— Game Masters (Math Masters, pp. 472–484) Щ— number cards 0–10 (4 of each from the Everything Math Deck, if available); counters; slates Щ— calculator (optional) Technology Assessment Management System Journal page 273 See the iTLG. Lesson 8 8 бњ 659 Getting Started Mental Math and Reflexes Math Message Have students write each mixed number as a fraction. Suggestions: Complete journal page 272. 2 5 1бЋЏ3бЋЏ бЋЏ3бЋЏ 7 34 3бЋЏ9бЋЏ бЋЏ9бЋЏ 4 46 6бЋЏ7бЋЏ бЋЏ7бЋЏ 7 87 8бЋЏ10бЋЏ бЋЏ10бЋЏ 4 29 5бЋЏ5бЋЏ бЋЏ5бЋЏ 5 29 3бЋЏ8бЋЏ бЋЏ8бЋЏ Study Link 8 7 Follow-Up бњ Have partners compare answers and resolve differences. Ask volunteers to write the incomplete version of their “What’s My Rule?” table for the class to solve. 1 Teaching the Lesson б¤ Math Message Follow-Up WHOLE-CLASS DISCUSSION (Math Journal 2, p. 272) Ask students why the hexagons in the last row of the example on the journal page are divided into sixths. Sample answer: To add the 3 in 3 П© бЋЏ56бЋЏ, you need a common denominator. A simple way is to think of each whole as бЋЏ66бЋЏ. Ask volunteers to share their solution strategies for Problems 1–8. б¤ Multiplying with WHOLE-CLASS ACTIVITY Mixed Numbers Ask students how they would use the partial-products method to calculate 6 ‫ ء‬4бЋЏ35бЋЏ. Discuss student responses as you summarize the following strategy: Student Page Date Time LESSON Review Converting Fractions to Mixed Numbers 8 8 бњ 1. Think of 4бЋЏ35бЋЏ as 4 П© бЋЏ35бЋЏ. Math Message You know that fractions larger than 1 can be written in several ways. Whole Rule Example: hexagon If a is worth 1, what is worth? 5 5 5 The mixed-number name is 3 бЋЏ6бЋЏ (3 бЋЏ6бЋЏ means 3 П© бЋЏ6бЋЏ). 23 The fraction name is бЋЏ6бЋЏ. Think sixths: 5 5 23 3 бЋЏ6бЋЏ, 3 П© бЋЏ6бЋЏ, and бЋЏ6бЋЏ are different names for the same number. Write the following mixed numbers as fractions. 13 бЋЏ бЋЏ 5 бЋЏ5бЋЏ 3 3 1. 2 бЋЏ5бЋЏ П 2 3. 1 бЋЏ3бЋЏ П 3бЋЏ 9 бЋЏ 8 7 2. 4 бЋЏ8бЋЏ П 6 4. 3 бЋЏ4бЋЏ П 18 бЋЏ бЋЏ 4 , or 9 бЋЏбЋЏ 2 Write the following fractions as mixed or whole numbers. 1 2 бЋЏ3бЋЏ 7 5. бЋЏ3бЋЏ П 18 7. бЋЏ4бЋЏ П 6 6. бЋЏ1бЋЏ П бЋЏ2бЋЏ 4 4 , or 4 бЋЏ1бЋЏ 2 9 8. бЋЏ3бЋЏ П 6 3 Add. 7 7 9. 2 П© бЋЏ8бЋЏ П 3 11. 3 П© бЋЏ5бЋЏ П 2 бЋЏ8бЋЏ 3 бЋЏ3бЋЏ 5 3 3 10. 1 П© бЋЏ4бЋЏ П 1 12. 6 П© 2 бЋЏ3бЋЏ П 1бЋЏ4бЋЏ 1 8 бЋЏ3бЋЏ 272 Math Journal 2, p. 272 660 бџ Calculate the partial products and add. Unit 8 Fractions and Ratios 6 ‫ ء‬4бЋЏ35бЋЏ П 6 ‫( ء‬4 П© бЋЏ35бЋЏ) 2. Write the problem as the sum of partial products. П (6 ‫ ء‬4) П© (6 ‫ ء‬ᎏ35бЋЏ) 3. Calculate the partial products. П 24 П© бЋЏ15бЋЏ8 4. Convert бЋЏ15бЋЏ8 to a mixed number. П 24 П© 3бЋЏ35бЋЏ 5. Add. П 27бЋЏ35бЋЏ Ongoing Assessment: Informing Instruction Watch for students who have difficulty organizing partial products when multiplying two mixed numbers. Show them the diagram below, and have them write the partial products in a column. 3 4 3 2‫ء‬3 П 6 П 6 2в€—3 2 2в€— 2 бЋЏбЋЏ 3 3 4 2 ‫ ء‬ᎏ34бЋЏ П 2 бЋЏбЋЏ 3 2 3 2 3 2 3 в€—3 в€— ‫ء‬3 П вЂ« ء‬ᎏ43бЋЏ П 6 бЋЏбЋЏ 3 6 бЋЏбЋЏ 4 6 бЋЏбЋЏ 12 П 2 П 1бЋЏ12бЋЏ П 3 4 1 бЋЏбЋЏ 2 9бЋЏ22бЋЏ, or 10 Ask students how they might use improper fractions to solve the problem. Again, discuss student responses as you summarize the following strategy: бџ Convert whole numbers and mixed numbers to improper fractions. 1. Think of 6 as бЋЏ61бЋЏ and 4бЋЏ35бЋЏ as бЋЏ25бЋЏ3. 6 ‫ ء‬4бЋЏ35бЋЏ 2. Rewrite the problem as fraction multiplication. П бЋЏ61бЋЏ ‫ ء‬ᎏ253бЋЏ 6‫ء‬23 3. Use a fraction multiplication algorithm. бЋЏ ПбЋЏ 1‫ء‬5 4. Multiply. 138 бЋЏ ПбЋЏ 5 5. Simplify the answer by converting 138 бЋЏбЋЏ to a mixed number. 5 П 27бЋЏ35бЋЏ Ask students to suggest advantages and disadvantages for each method. Expect a variety of responses. Sample answers: The partial-products method lets you work with smaller numbers but has more calculations. The improper-fraction method lets you multiply fractions where one of the denominators will be one, but you have a larger number to divide to simplify the answer. Ask students to work through two or three additional examples, using either of the above strategies or others of their own choosing. After each problem, ask volunteers to share their solution strategies. Suggestions: в—Џ 4 ‫ ء‬ᎏ35бЋЏ 2бЋЏ25бЋЏ в—Џ 2бЋЏ14бЋЏ ‫ ء‬ᎏ23бЋЏ 1бЋЏ12бЋЏ в—Џ 2бЋЏ23бЋЏ ‫ ء‬3 8 Student Page Date Time LESSON Multiplying Fractions and Mixed Numbers 8 8 бњ Using Partial Products Example 2: Example 1: 1 1 1 1 2 бЋЏ3бЋЏ ‫ ء‬2 бЋЏ2бЋЏ П (2 П© бЋЏ3бЋЏ) ‫( ء‬2 П© бЋЏ2бЋЏ) 1 2 1 2 3 бЋЏ4бЋЏ ‫ ء‬ᎏ5бЋЏ П.(3 П© бЋЏ4бЋЏ) ‫ ء‬ᎏ5бЋЏ 2 6 2‫ء‬2П 4 3 ‫ ء‬ᎏ5бЋЏ П.бЋЏ5бЋЏ П 2 ‫ ء‬ᎏ2бЋЏ П 1 1 1 бЋЏбЋЏ 4 1 бЋЏбЋЏ 3 ‫ء‬2П 2 бЋЏбЋЏ 3 1 бЋЏбЋЏ 3 1 бЋЏбЋЏ 2 ‫ء‬ П 1 1 бЋЏ5бЋЏ 2 1 2 ‫ ء‬ᎏ5бЋЏ П.бЋЏ20бЋЏ П П© бЋЏ1бЋЏ 0 3 1 бЋЏ10бЋЏ 1 П© бЋЏ6бЋЏ 5 5 бЋЏ6бЋЏ Converting Mixed Numbers to Fractions Example 3: 1 1 Example 4: 7 5 2 бЋЏ3бЋЏ ‫ ء‬2 бЋЏ2бЋЏ П бЋЏ3бЋЏ ‫ ء‬ᎏ2бЋЏ 1 2 13 2 3 бЋЏ4бЋЏ ‫ ء‬ᎏ5бЋЏ П бЋЏ4бЋЏ ‫ ء‬ᎏ5бЋЏ 35 5 П бЋЏ6бЋЏ П 5 бЋЏ6бЋЏ 6 3 26 П бЋЏ20бЋЏ П 1 бЋЏ20бЋЏ П 1 бЋЏ10бЋЏ Solve the following fraction and mixed-number multiplication problems. 7 77 43 бЋЏбЋЏ, or 7 бЋЏбЋЏ бЋЏбЋЏ, or 1 1 3 1 10 10 8 1. 3 бЋЏ2бЋЏ ‫ ء‬2 бЋЏ5бЋЏ П 2. 10 бЋЏ4бЋЏ ‫ ء‬ᎏ2бЋЏ П 3. The back face of a calculator has an area of about 11 16 бЋЏ6бЋЏ4 in2. 4. The area of this sheet of notebook paper is about 5 ACMECALC INC. Model# JETSciCalc Serial# 143 58 " 84 ଙ 1 10 2 " in2. 7 28 " 8" 5. The area of this computer disk is about 5 13 бЋЏ1бЋЏ2 in2. 3 5бЋЏ8бЋЏ 6. The area of this 5 36 " 1 32 " flag is about 8бЋЏ165бЋЏ, or 8бЋЏ25бЋЏ yd2. 7. Is the flag’s area greater or less than that of your desk? 1 2 3 yd 3 3 5 yd Answers vary. 273 Math Journal 2, p. 273 Lesson 8 8 бњ 661 Student Page Date Time LESSON Track Records on the Moon and the Planets 8 8 бњ б¤ Multiplying Fractions and PARTNER ACTIVITY Mixed Numbers Every moon and planet in our solar system pulls objects toward it with a force called gravity. 2 In a recent Olympic games, the winning high jump was 7 feet 8 inches, or 7бЋЏ3бЋЏ feet. The winning pole vault was 19 feet. Suppose that the Olympics were held on Earth’s Moon, or on Jupiter, Mars, or Venus. What height might we expect for a winning high jump or a winning pole vault? (Math Journal 2, pp. 273 and 274) Assign both journal pages. Encourage students to consider the numbers in each problem and then to use the method that is most efficient for that problem. Circulate and assist. 1. On the Moon, one could jump about 6 times as high as on Earth. What would be the height of the winning … 46 high jump? About feet 114 pole vault? About feet 3 2. On Jupiter, one could jump about бЋЏ8бЋЏ as high as on Earth. What would be the height of the winning … 69 7 бЋЏбЋЏ бЋЏбЋЏ high jump? About 24 , or 2 8 feet pole vault? About 3. On Mars, one could jump about 57 бЋЏбЋЏ, 8 or 7бЋЏ18бЋЏ feet 2 2 бЋЏ3бЋЏ times as high as on Earth. What would be the height of the winning … 152 184 4 бЋЏбЋЏ, бЋЏбЋЏ, or 20 бЋЏбЋЏ 9 feet high jump? About 9 pole vault? About 3 or 50 бЋЏ23бЋЏ feet Ongoing Assessment: Recognizing Student Achievement 1 4. On Venus, one could jump about 1 бЋЏ7бЋЏ times as high as on Earth. What would be the height of the winning … 152 184 16 бЋЏбЋЏ, бЋЏбЋЏ, or 8 бЋЏбЋЏ 21 feet high jump? About 21 pole vault? About 7 or 21 бЋЏ57бЋЏ feet Journal Page 273 Problem 5 ଙ Use journal page 273, Problem 5 to assess students’ understanding of multiplication with mixed numbers. Have students complete an Exit Slip (Math Masters, 414) for the following: Explain how you solved Problem 5 on journal page 273. Students are making adequate progress if they correctly reference using partial products, improper fractions, or a method of their own. 5. Is Jupiter’s pull of gravity stronger or weaker than Earth’s? Explain your reasoning. Sample answer: Because you can’t jump as high on Jupiter as you can on Earth, the gravity pulling you back on Jupiter must be stronger. Try This 6. The winning pole-vault height given above was rounded to the nearest whole 1 number. The actual winning height was 19 feet бЋЏ4бЋЏ inch. If you used this actual [Operations and Computation Goal 5] measurement, about how many feet high would the winning jump be … 17 бЋЏ 114бЋЏ18бЋЏ 7бЋЏ 128 on the Moon? on Jupiter? 50 бЋЏ11бЋЏ38 21бЋЏ3412бЋЏ on Mars? on Venus? 274 Math Journal 2, p. 274 2 Ongoing Learning & Practice б¤ Using Unit Fractions to Find INDEPENDENT ACTIVITY a Fraction of a Number (Math Journal 2, p. 275) Students practice using unit fractions to find the fraction of a number. б¤ Math Boxes 8 8 Student Page Date бњ Time LESSON (Math Journal 2, p. 276) Finding Fractions of a Number 8 8 бњ One way to find a fraction of a number is to use a unit fraction. A unit fraction is a fraction with 1 in the numerator. You can also use a diagram to help you understand the problem. 7 1 бЋЏбЋЏ 8 of 32 is 4. So Mixed Practice Math Boxes in this lesson are paired with Math Boxes in Lesson 8-6. The skill in Problem 5 previews Unit 9 content. 32 Example: What is бЋЏ8бЋЏ of 32? 7 бЋЏбЋЏ 8 of 32 is 7 ‫ ء‬4 П 28. ? Solve. 1 1. бЋЏ5бЋЏ of 75 П 1 4. бЋЏ8бЋЏ of 120 П 15 15 2 2. бЋЏ5бЋЏ of 75 П 3 5. бЋЏ8бЋЏ of 120 П 30 45 4 3. бЋЏ5бЋЏ of 75 П 5 6. бЋЏ8бЋЏ of 120 П 60 75 Solve Problems 7–18. They come from a math book that was published in 1904. 1 2 First think of бЋЏ3бЋЏ of each of these numbers, and then state бЋЏ3бЋЏ of each. 7. 9 10. 3 6 2 8. 6 11. 21 4 14 9. 12 12. 30 8 20 1 3 First think of бЋЏ4бЋЏ of each of these numbers, and then state бЋЏ4бЋЏ of each. 13. 32 16. 24 24 18 14. 40 17. 20 30 15 15. 12 18. 28 9 21 19. Lydia has 7 pages of a 12-page song memorized. Has she memorized more 2 than бЋЏ3бЋЏ of the song? No 1 20. A CD that normally sells for $15 is on sale for бЋЏ3бЋЏ off. What is the sale price? $10 1 21. Christine bought a coat for бЋЏ4бЋЏ off the regular price. She saved $20. What did she pay for the coat? $60 22. Seri bought 12 avocados on sale for $8.28. What is the unit price, the cost for 1 avocado? $0.69 275 Math Journal 2, p. 275 662 INDEPENDENT ACTIVITY Unit 8 Fractions and Ratios Writing/Reasoning Have students write a response to the following: Explain how to use the division rule for finding equivalent fractions to solve Problem 4b. Sample answer: The division rule states that you can rename a fraction by dividing the numerator and the denominator by the same number. I divided the numerator and the denominator by 2 to rename the 4 4П¬ 2 2 бЋЏ бЋЏбЋЏ fraction бЋЏ50бЋЏ; бЋЏ 50П¬2 П 25 Student Page б¤ Study Link 8 8 бњ INDEPENDENT ACTIVITY (Math Masters, p. 237) Date Time LESSON Math Boxes 8 8 бњ 1. a. Write a 7-digit numeral that has 5 in the ten-thousands place, 6 in the tens place, 9 in the ones place, 7 in the hundreds place, 3 in the hundredths place, and 2 in all the other places. b. Write this numeral in expanded notation. Home Connection Students practice multiplying fractions and mixed numbers. They find the areas of rectangles, triangles, and parallelograms. 52,769.23 50,000 П© 2,000 П© 700 П© 60 П© 9 П© 0.2 П© 0.03 4 1 3. Ellen played her guitar 2бЋЏбЋЏ hours on 3 Saturday and 1бЋЏ1бЋЏ hours on Sunday. How 4 2. Write 3 equivalent fractions for each number. Sample 4 6 8 бЋЏбЋЏ бЋЏбЋЏ бЋЏбЋЏ 14 21 28 6 9 12 3 бЋЏбЋЏ бЋЏбЋЏ бЋЏбЋЏ b. бЋЏбЋЏ 10 15 20 5 10 15 20 5 бЋЏбЋЏ бЋЏбЋЏ бЋЏбЋЏ c. бЋЏбЋЏ 16 24 32 8 2 4 6 20 бЋЏбЋЏ бЋЏбЋЏ бЋЏбЋЏ d. бЋЏбЋЏ 3 6 9 30 5 1 10 25 бЋЏбЋЏ бЋЏбЋЏ бЋЏбЋЏ e. бЋЏбЋЏ 2 10 20 50 , , , , , 2 a. бЋЏбЋЏ 7 3 Differentiation Options answers: much longer did she play on Saturday? 2 бЋЏ13бЋЏ ПЄ 1бЋЏ14бЋЏ П h 1 бЋЏбЋЏ hours h П 1 12 Answer: , , , , , Number model: 59 READINESS б¤ Ordering Improper Fractions SMALL-GROUP ACTIVITY 5 2 4 b. бЋЏбЋЏ П 50 6 c. бЋЏбЋЏ 20 scalene triangle. 2 8 a. бЋЏбЋЏ П 20 15–30 Min To review converting between fractions and mixed numbers and finding common denominators, have students order a set of improper fractions. Write the following fractions on the board: 7 4 7 11 бЋЏбЋЏ, бЋЏбЋЏ, бЋЏбЋЏ, and бЋЏбЋЏ. Ask students to suggest how to order the fractions 2 1 3 6 from least to greatest. Expect that students will suggest the same strategies they used with proper fractions, such as putting the numbers in order and then comparing them to a reference. Use their responses to discuss and demonstrate the following methods: 71 5. Use your Geometry Template to draw a 4. Complete. 25 3 П How does the scalene triangle differ from other triangles on the Geometry Template? 10 1 2 d. бЋЏбЋЏ П 18 9 None of the sides are the same length. 108 109 134 276 Math Journal 2, p. 276 бџ Rename each improper fraction as an equivalent fraction with a common denominator. Ask students what common denominator to use. Sample answer: Use 6 because the other denominators are all factors of 6. Have volunteers rename the fractions and write the equivalent fractions on the board underneath the first list of fractions. бЋЏ26бЋЏ1, бЋЏ26бЋЏ4, бЋЏ16бЋЏ4, бЋЏ16бЋЏ1 бџ Write each fraction as a mixed number. Ask volunteers to write the mixed numbers on the board underneath the second list. 3бЋЏ12бЋЏ, 4, 2бЋЏ13бЋЏ, 1бЋЏ56бЋЏ Ask students to order the 3 lists on their slates. бЋЏ16бЋЏ1, бЋЏ73бЋЏ, бЋЏ72бЋЏ, бЋЏ41бЋЏ; 5 11 14 21 24 1 1 бЋЏбЋЏ, бЋЏбЋЏ, бЋЏбЋЏ, бЋЏбЋЏ; and 1бЋЏбЋЏ, 2бЋЏбЋЏ, 3бЋЏбЋЏ, 4 Discuss any difficulties or curiosities 6 6 6 6 3 2 6 that students encountered. Study Link Master Name Date STUDY LINK 88 1. Multiply. 46 бЋЏбЋЏ, 5 бЋЏ3бЋЏ Вє бЋЏ2бЋЏ П 24 or 1бЋЏ112бЋЏ1 85 бЋЏбЋЏ, 5 1 c. 4 бЋЏбЋЏ Вє бЋЏбЋЏ П 24 3бЋЏ12бЋЏ34 a. 4 6 or 6 4 296 бЋЏбЋЏ, 1 3 e. 3 бЋЏбЋЏ Вє 1 бЋЏбЋЏ П 60 12 EXTRA PRACTICE б¤ Playing Frac-Tac-Toe PARTNER ACTIVITY 2. Students play a favorite version of Frac-Tac-Toe to practice converting between fractions, decimals, and percents. or 5 5 b. бЋЏбЋЏ 8 Вє бЋЏ2бЋЏ П 5 10 бЋЏбЋЏ, 40 1 бЋЏбЋЏ 4 or 76–78 7 7 бЋЏ2бЋЏ4 175 бЋЏбЋЏ, 1 1 d. 2 бЋЏбЋЏ Вє 3 бЋЏбЋЏ П 24 or 364 бЋЏбЋЏ, 4 2 f. 2 бЋЏбЋЏ Вє 3 бЋЏбЋЏ П 40 or 9бЋЏ11бЋЏ0 3 4бЋЏ11бЋЏ45 8 5 8 Find the area of each figure below. Area of a Rectangle Area of a Triangle AПbВєh A П бЋЏ2бЋЏ Вє b Вє h 15–30 Min Area of a Parallelogram 1 a. (Student Reference Book, pp. 309–311; Math Masters, pp. 472–484) Time Multiplying Fractions and Mixed Numbers бњ b. AПbВєh c. 5 6 1 2 3 yd ft 3 2 4 ft 1 2 2 ft 2 3 3 yd Area П 3. 8бЋЏ59бЋЏ 4 ft yd2 Area П 5бЋЏ12бЋЏ ft2 2бЋЏ112бЋЏ Area П ft2 The dimensions of a large doghouse are 2 бЋЏ1бЋЏ times the dimensions of 2 a small doghouse. a. If the width of the small doghouse is 2 feet, what is the width of the large doghouse? 5 b. feet If the length of the small doghouse is 2 бЋЏ1бЋЏ feet, what is the length of the 4 large doghouse? 5 бЋЏбЋЏ 8 feet 5 2 ft 1 2 4 ft Math Masters, p. 237 Lesson 8 8 бњ 663
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