Transcript Dividing Fractions

Unit 2.2
Dividing
Fractions!!!!
2.7 Dividing Fractions
Objectives
1. Find the reciprocal of a fraction.
2. Divide fractions.
3. Solve application problems in which fractions
are divided.
Slide 2.7- 2
7
8
8
7
Reciprocal
Slide 2.7- 3
Parallel
Example 1
Finding Reciprocals
Find the reciprocal of each fraction.
5
a.
6
6
The reciprocal is .
5
6
b.
7
7
The reciprocal is .
6
4
c.
9
9
The reciprocal is .
4
d. 2
1
The reciprocal is .
2
Slide 2.7- 4
Slide 2.7- 5
Slide 2.7- 6
Dividing One Fraction by Another
Divide. Write answers in lowest terms and as
mixed numbers where possible.
1 3

2 4
3
4
is .
The reciprocal of
4
3
Reciprocals
2
1 3 1 4
  
2 4 2 3
1
1 3 1 4
  
2 4 2 3
Change division to multiplication
1 2

1 3
2

3
Slide 2.7- 7
Dividing One Fraction by Another
Divide
7
8
1
2
7
8
1
2
7 1
 
8 2
7 21
 
8 1
4
7 1

4 1
7
3

1
4
4
Slide 2.7- 8
Dividing with a Whole Number
Divide. Write all answers in lowest terms and as
whole or mixed numbers where possible.
a. 9 
1
4
Write 9 as 9/1. Use the reciprocal of ¼ which is
4/1.
1 9 4 9  4 36
9   

 36
4 1 1 1 1
1
Slide 2.7- 9
Dividing with a Whole Number
Divide. Write all answers in lowest terms and as whole or mixed numbers where
possible.
5
b.  4
8
Write 4 as 4/1. The reciprocal of 4/1 is ¼.
5
5 1 5 1
5
4   

8
8 4 84
32
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
Applying Fraction Skills
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.
4
32
20
8
5 20 8
 32

 1 
20  

1
1 5
8
1 5
Slide 2.7- 12
Applying Fraction Skills
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.
Slide 2.7- 13