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Chapter 2 Multiplying and Dividing Fractions Copyright © 2011 Pearson Education, Inc. Publishing as Prentice Hall. 2.4 Multiplying Fractions and Mixed Numbers Copyright © 2011 Pearson Education, Inc. Publishing as Prentice Hall. Multiplying Fractions Multiplying Fractions To multiply two fractions, multiply the numerators and multiply the denominators. If a, b, c, and d represent positive whole numbers we have a c a c b d bd Copyright © 2011 Pearson Education, Inc. Publishing as Prentice Hall. Martin-Gay, Basic Mathematics, 4e 3 Examples Multiply. a. 2 3 2 3 6 7 5 75 35 1 1 1 1 1 b. 33 11 3 11 3 c. 8 2 4 21 3 7 Copyright © 2011 Pearson Education, Inc. Publishing as Prentice Hall. Martin-Gay, Basic Mathematics, 4e 4 Examples Multiply and simplify. a. 3 8 3 2 2 2 6 4 11 2 2 11 11 2 3 2 7 1 2 3 14 b. 7 2 2 2 3 5 10 7 8 15 Copyright © 2011 Pearson Education, Inc. Publishing as Prentice Hall. Martin-Gay, Basic Mathematics, 4e 5 Multiplying Fractions and Mixed Numbers or Whole Numbers Multiplying Fractions and Mixed Numbers of Whole Numbers To multiply with mixed numbers or whole numbers, first write any mixed or whole numbers as fractions and then multiply as usual. Copyright © 2011 Pearson Education, Inc. Publishing as Prentice Hall. Martin-Gay, Basic Mathematics, 4e 6 Examples Multiply. 8 7 2227 7 1 2 7 or 2 a. 2 3 3 8 3 2 2 2 3 3 8 b. 2 43 43 7 2 3 2 43 1 5 36 36 9 8 9 8 3 3 2 2 2 Copyright © 2011 Pearson Education, Inc. Publishing as Prentice Hall. Martin-Gay, Basic Mathematics, 4e 7 Example Multiply. 5 27 7 35 3 10 or 8 8 1 2 2 2 4 4 Copyright © 2011 Pearson Education, Inc. Publishing as Prentice Hall. Martin-Gay, Basic Mathematics, 4e 8 Example Multiply. Check by estimating. 20 5 2 1 5 2 25 2 1 9 4 9 4 3 3 2 2 25 7 or 2 9 9 Let’s check by estimating. 2 1 2 rounds to 2, 1 rounds to 1, and 2 · 1 = 2. 9 4 The estimate is close to the exact value, so our answer is reasonable. Copyright © 2011 Pearson Education, Inc. Publishing as Prentice Hall. Martin-Gay, Basic Mathematics, 4e 9 Example 1 An estimate for the measure of an adult’s wrist is 4 of the waist size. If Jorge has a 34-inch waist, estimate the size of his wrist. 34 1 17 2 1 17 or 8 1 2 1 4 1 2 2 2 1 Jorge’s wrist is about 8 inches. 2 Copyright © 2011 Pearson Education, Inc. Publishing as Prentice Hall. Martin-Gay, Basic Mathematics, 4e 10