Page 314 - Basic College Mathematics with Early Integers

S E C T I O N 4.2 I ADDING AND SUBTRACTING DECIMALS 291

Example 5 Subtract: 3.5 - 0.068. Check your answer. PRACTICE 5

Subtract. Check your answers.
Solution: 9
4 10 10 a. 5.8 - 3.92
3. 5 0 0 Insert two 0s.
b. 9.72 - 4.068
- 0. 0 6 8 Line up decimal points.
3. 4 3 2 Subtract.
Check: Recall that we can check a subtraction problem by adding.
3.432 Difference
+ 0.068 Subtrahend
3.500 Minuend
Work Practice 5

Example 6 Subtract: 85 - 17.31. Check your answer. PRACTICE 6
Subtract. Check your answers.
Solution: 14 9
7 4 10 10 a. 53 - 29.31
8 5 . 0 0 Check: 67.69 Difference b. 120 - 68.22
+ 17.31 Subtrahend
- 1 7 . 3 1
85.00 Minuend
6 7 . 6 9
Work Practice 6

Example 7 Subtract 3 from 6.98. Check your answer. PRACTICE 7
Subtract: 18 from 26.99
Solution: 6.98 Check: 3.98 Difference
-3.00 Insert two 0s. + 3.00 Subtrahend
3.98 6.98 Minuend
Work Practice 7

Example 8 Subtract: -5.8 - 1.7 PRACTICE 8
Subtract: -3.4 - 9.6
Solution: Recall from Chapter 2 that to subtract 1.7, we add the opposite of 1.7,
or -1.7. Thus
-5.8 - 1.7 =-5.8 + (-1.7) To subtract, add the opposite of 1.7, which is -1.7 .
Add the absolute values.
=–7.5.
Use the common negative sign.
Work Practice 8
Example 9 Subtract: -2.56 - (-4.01) PRACTICE 9

Subtract: -1.05 - (-7.23)
Solution: -2.56 - (-4.01) =-2.56 + 4.01 To subtract, add the opposite of -4.01,
which is 4.01.
Subtract the absolute values.
=1.45
The answer is positive since 4.01
has the larger absolute value.
Work Practice 9
Objective Estimating when Adding or Subtracting Decimals
Answers
To help avoid errors, we can also estimate to see if our answer is reasonable when 5. a. 1.88 b. 5.652
adding or subtracting decimals. Although only one estimate is needed per opera- 6. a. 23.69 b. 51.78
tion, we show two for variety. 7. 8.99 8. -13 9. 6.18