Page 222 - Basic College Mathematics with Early Integers

S E C T I O N 3.3 I MULTIPLYING AND DIVIDING FRACTIONS 199

For example,

multiply by reciprocal
# #
#
#
3 1 3 8 3 8 3 2 4 1 6
÷ = = # = # = or 6
4 8 4 1 4 1 4 1 1
1
Just as when you are multiplying fractions, always check to see whether the result
can be simplified when you divide fractions.

Examples Divide and simplify. PRACTICE 9–11
Divide and simplify.
#
7 2 7 9 7 9 63
9. , = # = = 3 14 8 2
#
8 9 8 2 8 2 16 9. , 10. ,
2 5 7 9
1
#
#
5 3 5 4 5 4 5 4 5 4 1
10. , = # = = = 11. ,
#
# #
16 4 16 3 16 3 4 4 3 12 9 2
1
#
2 1 2 2 2 2 4
11. , = # = =
#
5 2 5 1 5 1 5
Work Practice 9–11
When dividing by a fraction, do not look for common factors to divide out until
you rewrite the division as multiplication.
Do not try to divide out these two 2s.
#
1 2 1 3 3
÷= =
2 3 2 2 4

7 5
Example 12 Divide: - ,- PRACTICE 12
12 6
10 2
Solution: Recall that the quotient (or product) of two negative numbers is a Divide: - 4 , 9
positive number.
1
#
7 5 7 6 7 6 7
- ,- =- # - = =
#
#
12 6 12 5 2 6 5 10
1
Work Practice 12
2 3
Concept Check Which of the following is the correct way to divide by ?
5 4
Or are both correct? Explain.
5 3 2 4
a. # b. #
2 4 5 3

3 5 Answers
Concept Check Which is the correct way to divide by ? Explain.
5 12 15 36 8 45
9. 10. 11. 12. -
28 7 9 4
3 5 3 12 3 5 5 5
a. , = # b. , = #
5 12 5 5 5 12 3 12 Concept Check Answers
a. incorrect b. correct
a. correct b. incorrect