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Multiplying & Dividing Fractions

Multiplying & Dividing Fractions. September 17 , 2012. Vocabulary. Reciprocal - A number and its reciprocal have a product of 1. To find the reciprocal of a fraction, exchange the numerator and the denominator. Remember that an integer can be written as a fraction with a denominator of 1.

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Multiplying & Dividing Fractions

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  1. Multiplying & Dividing Fractions September 17, 2012

  2. Vocabulary • Reciprocal - A number and its reciprocalhave a product of 1. To find the reciprocal of a fraction, exchange the numerator and the denominator. Remember that an integer can be written as a fraction with a denominator of 1.

  3. Modeling Fraction Multiplication • Split your grid vertically into rectangles. The number of rectangles you have should match the denominator of the first fraction. Then shade the number of rectangles represented by the numerator. • Split your grid horizontallyinto rectangles. The number of rectangles you have should match the denominator of the second fraction. Then shade the number of rectangles represented by the numerator. • Your product is the number of squares shaded twice over the total number of squares in the grid. • Simplify if needed.

  4. Examples • 1. 2.

  5. Multiplying Fractions • Write all mixed numbers and whole numbers as improper fractions. • Simplify all numbers before multiplying – numerators can only simplify denominators and denominators can only simply numerators. • Multiply numerator by numerator and denominator by denominator. • If your answer is an improper fraction turn it into a mixed number.

  6. Examples • 3. 4.

  7. Examples • 5. 6.

  8. Question • I have the problem . I want to get the same answer, but instead of dividing 36 by something, I want to multiply it by something. What should I multiply by?

  9. Dividing Fractions • Write all mixed numbers and whole numbers as improper fractions. • Then, leave the first fraction alone, change the division to multiplication, and change the second fraction to its reciprocal – also known as SAME-CHANGE-FLIP • Multiply numerator by numerator and denominator by denominator. • If your answer is an improper fraction turn it into a mixed number.

  10. Examples • 7. 8.

  11. Examples • 9. 10.

  12. Examples • 11. Leah is making hair bows. She has a piece of ribbon that is feet long. Each bow requires feet strips of ribbon. How many bows can she make?

  13. Examples • 12. Ryan is building a model of a log home for his social studies class. He needs to have 125 logs and each log should be inches long. How many total inches of log does he need?

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