Virtual Math Girl: Module 5 (Student) Working with Common Denominators Answer Key Activity 1: Finding Common Multiples Numbers Lowest Common Multiple 20 15 5 30 60 9 54 18 6 54 10 30 20 60 104 26 52 13 104 Answers will vary Answers will vary. One acceptable response might include using the skill in finding a common denominator in order to add fractions. Virtual Math Girl: Module 5 – Answer Key © 2010 WBGU-­‐PBS. Permission is granted for non-­‐profit educational use. 1 Activity 2: Adding Fractions with Different Denominators 1 1 1 ––– + ––– + ––– = 3 4 12 1 1 1 ––– + ––– + ––– = 6 4 8 1 1 1 ––– + ––– + ––– = 7 3 6 2 ––– 3 1 1 1 ––– + ––– + ––– = 3 6 18 1 1 1 ––– + ––– + ––– = 5 15 10 1 1 1 ––– + ––– + ––– = 6 2 5 5 ––– 9 13 ––– 24 27 9 ––– = ––– 42 14 11 ––– 30 13 ––– 15 Virtual Math Girl: Module 5 – Answer Key © 2010 WBGU-­‐PBS. Permission is granted for non-­‐profit educational use. 2 Activity 3: Subtracting Fractions with Different Denominators 1 1 3 ––– – ––– = ––– 2 8 8 3 2 1 ––– – ––– = ––– 4 3 12 11 2 1 11 ––– – ––– – ––– = ––– 12 6 8 24 6 1 1 ––– – ––– = ––– 9 3 3 4 1 1 ––– – ––– = ––– 6 3 3 10 3 2 -­‐1 ––– – ––– – ––– = ––– 15 10 5 30 Virtual Math Girl: Module 5 – Answer Key © 2010 WBGU-­‐PBS. Permission is granted for non-­‐profit educational use. 3 Activity 4: Bike Route Worksheet and Solving Equations with Fractions Answers will vary. One acceptable answer might include: 1/2 + 2/4 + 2/8 + 7/16 + 3/8 + 1/8 + 6/16 + 3/4 = 3 and 5/16 Activity 5: Working with Improper Fractions and Mixed Numbers 27 ––– = 2 1/4 12 15 ––– = 1 1/2 10 37 ––– = 5 2/7 7 22 ––– = 3 1/7 7 57 ––– = 6 1/3 9 Answers may vary. One example of a correct response might be: An improper fraction has a numerator that is of a higher value than the denominator while a mixed number involves a whole number and a fraction. Answers will vary Virtual Math Girl: Module 5 – Answer Key © 2010 WBGU-­‐PBS. Permission is granted for non-­‐profit educational use. 4 Activity 6: Putting all Our Fraction Facts to Good Use (Extended Activity) Amount Item Number Item Needed 3 16 ounce package of hot dogs 1 16 ounce package of hot dogs 2 12 ounce cans of beans 6 12 ounce cans of beans 1 10 3/4 ounce can condensed tomato soup medium onion 3 10 3/4 ounce can condensed tomato soup medium onion 1 3 Amount Item 3 16 ounce package of hot dogs 6 12 ounce cans of beans 3 10 ¾ ounce can condensed tomato soup medium onion 3 Total Weight In Ounces 48 72 32 ¼ 12 48 72 32.25 12 ––– + ––– + –––– + ––– = 16 16 16 16 hot dogs beans soup onions 164.25 –––––– = 16 Total Weight improper fraction 10.27 pounds Total Weight mixed number Virtual Math Girl: Module 5 – Answer Key © 2010 WBGU-­‐PBS. Permission is granted for non-­‐profit educational use. 5