Page 64 - Basic College Mathematics with Early Integers

S E C T ION 1. 5 I ROUNDING AND ESTIMATING 41

mistake in calculating an exact amount. To estimate the sum below, round each
number to the nearest hundred and then add.
768 rounds to 800
1952 rounds to 2000
225 rounds to 200
+ 149 rounds to + 100
3100

The estimated sum is 3100, which is close to the exact sum of 3094.

Example 4 Round each number to the nearest hundred to find an estimated PRACTICE 4
sum. Round each number to
the nearest ten to find an
294
estimated sum.
625
1071 49
+ 349 25
32
Solution: 51
Exact: Estimate: + 98
294 rounds to 300
625 rounds to 600
1071 rounds to 1100
349 rounds to 300
2300
The estimated sum is 2300. (The exact sum is 2339.)
Work Practice 4

Example 5 Round each number to the nearest hundred to find an estimated PRACTICE 5
difference. Round each number to the
nearest thousand to find an
4725
estimated difference.
- 2879
3785
Solution: -2479
Exact: Estimate:
4725 rounds to 4700
-2879 rounds to -2900
1800
The estimated difference is 1800. (The exact difference is 1846.)
Work Practice 5

Objective Solving Problems by Estimating

Making estimates is often the quickest way to solve real-life problems when
solutions do not need to be exact.

Answers
4. 260 5. 2000