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Today we will review “Multiplying & Dividing Fractions”

Today we will review “Multiplying & Dividing Fractions”. Let’s Warm up:. 1) ¾ + ¼ =1. 2) 3/5 – 1/4 =7/20. 4) ½ + ¾ - ¼ =1. 3) 5/6 – 2/5 =13/30. Estimating Products. Estimate using Compatible Numbers These are numbers that are easy to divide mentally Estimate ¼ x 13

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Today we will review “Multiplying & Dividing Fractions”

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  1. Today we will review “Multiplying & Dividing Fractions” CONFIDENTIAL

  2. Let’s Warm up:. 1) ¾ + ¼ =1 2) 3/5 – 1/4 =7/20 4) ½ + ¾ - ¼ =1 3) 5/6 – 2/5 =13/30 CONFIDENTIAL

  3. Estimating Products • Estimate using Compatible Numbers • These are numbers that are easy to divide mentally • Estimate ¼ x 13 • ¼ x 13 means ¼ of 13 • Find a number close to13 that is a multiple of 4. • ¼ x 13 ¼ x 12 • ¼ x 12 = 3 • So, ¼ x 13 is about 3. 12 and 4 are compatible numbers since 12 ÷ 4 = 3 12 ÷ 4 = 3 CONFIDENTIAL

  4. Estimating Products • Your Turn! • Estimate 2/5 x 11 = about 4 CONFIDENTIAL

  5. Estimating Products • Estimate by Rounding to 0, ½, or 1. • Estimate 1/3 x 7/8 • 1/3 x 7/8 ½ x 1 • ½ x 1 = ½ • So, 1/3 x 7/8 is about ½. 1/3 is about 1/2 7/8 is about 1 1/3 7/8 1 0 1/2 CONFIDENTIAL

  6. Estimating Products • Your Turn! • Estimate 5/8 x 9/10 = ½ x 1 = ½ CONFIDENTIAL

  7. Estimating Products • Estimating with Mixed Numbers • 11 ¾ x 8 1/6 • Round each number to the nearest whole number • 11 ¾ x 8 1/6 12 x 8 = 96 Round 11 ¾ to 12 Round 8 1/6 to 8 CONFIDENTIAL

  8. Multiplying Fractions • To multiply fractions, multiply the numerators and multiply the denominators • a x c = a x c b d b x d where b and d are not 0 • 2 x 1 = 2 x 1 = 2 5 2 5 x 2 10 CONFIDENTIAL

  9. Multiplying Fractions • Your Turn • Find 1/3 x ¼=1/12 CONFIDENTIAL

  10. Multiplying Fractions • Multiplying Fractions and Whole Numbers • First write the whole number as a fraction • Example; Find 3/5 x 4 • 3/5 x 4 = 3/5 x 4/1 = 3 x 4 5 x 1 = 12 or 2 2/5 5 Write 4 as 4/1 Multiply Simplify CONFIDENTIAL

  11. Multiplying Fractions • Your Turn • 2/3 x 6= 4 CONFIDENTIAL

  12. Multiplying Fractions • Simplify before Multiplying • Find ¾ x 5/6 • ¾ x 5/6 = 3 x 5 = 3 x 5 4 x 6 4 x 6 = 5 8 1 Divide both the numerator and the denominator by 3 2 The numerator 3 and denominator 6 have a common factor 3 CONFIDENTIAL

  13. Multiplying Fractions • Find 5/6 x 9/10 = 3/4 CONFIDENTIAL

  14. Multiplying Fractions • Evaluate Expressions • Evaluate ab if a = 2/3 and b = 3/8 • ab = 2/3 x 3/8 = 2 x 3 3 x 8 = 1 4 Replace a with 2/3 and b with 3/8 The GCF of 2 and 8 is 2. The GCF of 3 and 3 is 3. Divide both the numerator and denominator by 2 and then by 3. 1 1 1 4 CONFIDENTIAL

  15. Multiplying Fractions • Evaluate 3 c if c = 2 4 5 = 3/10 CONFIDENTIAL

  16. Multiplying Mixed Numbers • To multiply mixed numbers, write the mixed numbers as improper fractions • Then multiply as with fractions • Find ¼ x 4 4/5 4 Divide 24 and 4 by their GCF, 4 1 CONFIDENTIAL

  17. Multiplying Mixed Numbers • Your Turn • Find 2/3 x 2 ½ = 1 2/3 CONFIDENTIAL

  18. Multiplying Mixed Numbers • Your Turn • Find 2 ½ x 2 ¼ = 5/2 x 9/4 = 45/8 = 5 5/8 CONFIDENTIAL

  19. Dividing Fractions • To divide by a fraction, multiply by its reciprocal • Any two numbers whose product is 1 are called reciprocals. • 5 x 1/5 = 1; so the reciprocal of 5 is 1/5 • To find the reciprocal of a fraction, invert the fraction. That is, switch the numerator and denominator. • Reciprocal of 2/3 is 3/2 CONFIDENTIAL

  20. Dividing Fractions • Find 1/8 ÷ 3/4 CONFIDENTIAL

  21. Dividing Fractions • Your Turn • Divide ¼ ÷ 3/8 = 2/3 CONFIDENTIAL

  22. Dividing Mixed Numbers • Write mixed numbers as improper fractions • Multiply by the reciprocal • Simplify CONFIDENTIAL

  23. Dividing Mixed Numbers • Your Turn • Divide. Write in simplest form. CONFIDENTIAL

  24. Let us take a break! CONFIDENTIAL

  25. Game • Click me Let us see how much you score on this one! CONFIDENTIAL

  26. Assessment • Estimate 1/8 x 15=1/8 x 16 = 2 • Estimate ¾ x 21= ¾ x 20 = 15 CONFIDENTIAL

  27. Assessment • Multiply. Write in simplest form. 1/8 x ½ = 1/16 • Multiply. Write in simplest form. 4/5 x 10 = 8 CONFIDENTIAL

  28. Assessment • Multiply. Write in simplest form. • Multiply. Write in simplest form. CONFIDENTIAL

  29. Assessment • Divide. Write in simplest form. • Divide. Write in simplest form. CONFIDENTIAL

  30. Assessment • Divide. Write in simplest form. • Divide. Write in simplest form. CONFIDENTIAL

  31. Good Job! • You have learned a lot today!!! CONFIDENTIAL

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