Page 232 - Basic College Mathematics with Early Integers

S E C T I O N 3.4 I ADDING AND SUBTRACTING LIKE FRACTIONS, LEAST COMMON DENOMINATOR 209

3 7
Example 7 Subtract: - PRACTICE 7
4 4
2 7
Subtract: -
3 7 3 - 7 3 + 1-72 -4 5 5
Solution: - = = = =-1
4 4 4 4 4
Work Practice 7

3 6 3
Example 8 Subtract: - -
7 7 7 PRACTICE 8

3 6 3 3 - 6 - 3 -6 6 4 6 3
Solution: - - = = or - Subtract: - -
7 7 7 7 7 7 11 11 11
Work Practice 8

-6 6 6 6
Recall that =- aAlso, =- , if needed.b
7 7 -7 7

Objective Adding or Subtracting Given Fractional
Replacement Values

3 8
Example 9 Evaluate y - x if x =- and y =- . PRACTICE 9
10 10
10
Solution: Be very careful when replacing and with replacement values.yx Evaluate x + y if x =- 12 and
5
8 3 3 8 y = .
y - x = - - a- b Replace x with - and y with - . 12
10 10 10 10
-8 - (-3)
=
10
#
-5 -1 5 -1 1
= = = or -
#
10 2 5 2 2
Work Practice 9

Objective Solving Problems by Adding or Subtracting
Like Fractions

Many real-life problems involve finding the perimeters of square- or rectangular- PRACTICE 10
shaped figures such as pastures, swimming pools, and so on. We can use our knowl-
edge of adding fractions to find perimeters. Find the perimeter of the
square.

Example 10 Find the perimeter of the rectangle.
3 mile
20
2 inch
15
4
15 inch Answers
5 5 3
Continued on next page 7. -1 8. - 9. - 10. mi
11 12 5