Today we will review “Multiplying & Dividing Fractions”

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

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

18. Multiplying Mixed Numbers • Your Turn • Find 2 ½ x 2 ¼ 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 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’s take a break! CONFIDENTIAL

25. CONFIDENTIAL

26. Assessment • Estimate 1/8 x 15 • Estimate ¾ x 21 CONFIDENTIAL

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