Unit 2.2

Dividing Fractions!!!!

2.7 Dividing FractionsObjectives

Slide 2.7- 2

1. Find the reciprocal of a fraction.

2. Divide fractions.

3. Solve application problems in which fractions are divided.

Slide 2.7- 3

7 8 8 7

Reciprocal

Find the reciprocal of each fraction.

a.

b.

c.

d. 2

ParallelExample 1 Finding Reciprocals

The reciprocal is 5667

Slide 2.7- 4

65

.

The reciprocal is 76

.

49

The reciprocal is 94

.

The reciprocal is 12

.

Slide 2.7- 5

Slide 2.7- 6

Divide. Write answers in lowest terms and as mixed numbers where possible.

Dividing One Fraction by Another

The reciprocal of

1 32 4

1 1

42 23 4

3

Slide 2.7- 7

3 4 is .4 3

Reciprocals

Change division to multiplication

1 3 1 42 4 2 3

2

1

1 21 3

23

Divide7812

7 18 2

7 28 1

7 14 1

314

Slide 2.7- 8

Dividing One Fraction by Another

7812

1

4

74

Divide. Write all answers in lowest terms and as whole or mixed numbers where possible.

a.

Dividing with a Whole Number

194

Write 9 as 9/1. Use the reciprocal of ¼ which is 4/1.

99 1 44 11

9 41 1

36 361

Slide 2.7- 9

Divide. Write all answers in lowest terms and as whole or mixed numbers where possible.

b.

Dividing with a Whole Number

5 48

Write 4 as 4/1. The reciprocal of 4/1 is ¼.

5 5 1448 8

5 18 4

532

Slide 2.7- 10

The manager of a local feed mill must fill a 20-gallon container with feed. He only has a 5/8 gallon container to use. How many times must he fill the 5/8 gallon container and empty it into the 20-gallon container?

Step 1 Read the problem. We need the number of times the manager needs to use a 5/8 gallon container in order to fill a 20-gallon container.

Step 2 Work out a plan. We can solve the problem by finding the number of times 20 can be divided by 5/8.

Slide 2.7- 11

The manager of a local feed mill must fill a 20-gallon container with feed. He only has a 5/8 gallon container to use. How many times must he fill the 5/8 gallon container and empty it into the 20-gallon container?

Step 3 Estimate a reasonable answer. Round 5/8 to 1 gallon. He would need to use the container about 20 times.

Step 4 Solve the problem.

Applying Fraction Skills

5 20 8208 1 5

Slide 2.7- 12

20

48

1 5 1

32 321

The manager of a local feed mill must fill a 20-gallon container with feed. He only has a 5/8 gallon container to use. How many times must he fill the 5/8 gallon container and empty it into the 20-gallon container?

Step 5 State the answer. The manager must fill the container 32 times.

Step 6 Check. The exact answer is close to our estimate.

Applying Fraction Skills

Slide 2.7- 13