Page 168 - Basic College Mathematics with Early Integers

S E C T I O N 2.5 I MULTIPLYING AND DIVIDING INTEGERS 145

Examples Divide, if possible. PRACTICE 13–14

0 Divide, if possible.
#
13. = 0 because 0 -5 = 0
-5 -1 0
13. 14.
-7 0 -12
14. is undefined because there is no number that gives a product of -7 when
0
multiplied by 0.
Work Practice 13–14

Objective Evaluating Expressions

Next, we practice evaluating expressions given integer replacement values.

Example 15 Evaluate xy for x =-2 and y = 7. PRACTICE 15
Evaluate xy for x = 5 and
#
Solution: Recall that xy means x y. y =-9.
Replace x with -2 and y with 7.
#
xy = -2 7
=-14
Work Practice 15

x
Example 16 Evaluate for x =-24 and y = 6. PRACTICE 16
y
x -24 x
Solution: = Replace x with -24 and y with 6. Evaluate for x =-12 and
y
y 6
y =-4.
=-4
Work Practice 16
PRACTICE 17
A card player had a score of
Objective Solving Problems by Multiplying -12 for each of four games.
and Dividing Integers Find her total score.

Many real-life problems involve multiplication and division of signed numbers.

Example 17 Calculating a Total Golf Score

A professional golfer finished seven strokes under par 1-72 for each of three days
of a tournament.What was his total score for the tournament?
Solution:

1. UNDERSTAND. Read and reread the problem. Although the key word is
“total,” since this is repeated addition of the same number, we multiply.
In words: golfer’s total number of score
2. TRANSLATE.
score = days # each day
Translate: golfer’s T T T # T
T
total = 3 1-72
#
3. SOLVE: 3 1-72 = -21
4. INTERPRET. Check and state your conclusion:The golfer’s total score was -21,
or 21 strokes under par. Answers
Work Practice 17 13. undefined 14. 0 15. -45
16. 3 17. -48