Page 158 - Basic College Mathematics with Early Integers

S E C T I O N 2.4 I SUBTRACTING INTEGERS 135

Example 12 Evaluate 2a - b for a = 8 and b =-6. PRACTICE 12
Evaluate 3y - z for y = 9 and
Solution: Watch your signs carefully! z =-4.
b
2a - Watch carefully
T T when replacing variables in
T e
#
= 2 8 - 1-62 Replace a with 8 and b with -6. the expression 2a - b. Make
sure that all symbols are
= 16 + 6 Multiply.
inserted and accounted for.
= 22 Add.
Work Practice 12
Objective Solving Problems by Subtracting Integers
Solving problems often requires subtraction of integers.

Example 13 Finding a Change in Elevation PRACTICE 13
The highest point in the United States is the top of Mount McKinley, at a height of The highest point in Asia is the
20,320 feet above sea level. The lowest point is Death Valley, California, which is top of Mount Everest, at a
282 feet below sea level. How much higher is Mount McKinley than Death Valley? height of 29,028 feet above sea
(Source: U.S. Geological Survey) level.The lowest point is the
Dead Sea, which is 1312 feet
Solution: below sea level. How much
1. UNDERSTAND. Read and reread the problem.To find “how much higher,” we higher is Mount Everest than
subtract. Don’t forget that since Death Valley is 282 feet below sea level, we the Dead Sea? (Source:
represent its height by -282. Draw a diagram to help visualize the problem. National Geographic Society)

Mt. McKinley

20,320 feet

Sea level
Death Valley
282 feet

2. TRANSLATE.

how much higher height of height of
In words: = minus
is Mt. McKinley Mt. McKinley Death Valley
T T T T T
how much higher
Translate: = 20,320 - 1-2822
is Mt. McKinley
3. SOLVE:
20,320 - 1-2822 = 20,320 + 282 = 20,602
4. INTERPRET. Check and state your conclusion: Mount McKinley is 20,602 feet
higher than Death Valley.
Work Practice 13

Answers
12. 31 13. 30,340 ft