Page 62 - Basic College Mathematics with Early Integers

1.5 ROUNDING AND ESTIMATING Objectives

Round Whole Numbers.

Objective Rounding Whole Numbers Use Rounding to Estimate Sums
and Differences.
Rounding a whole number means approximating it. A rounded whole number is
often easier to use, understand, and remember than the precise whole number. For Solve Problems by Estimating.
example, instead of trying to remember the Minnesota state population as
5,197,621, it is much easier to remember it rounded to the nearest million: 5,000,000,
or 5 million people. (Source:World Almanac)
Minnesota
Recall from Section 1.2 that the line below is called a number line. To graph a Population:
whole number on this number line, we darken the point representing the location of 5,197,621
or
the whole number. For example, the number 4 is graphed below. about
5 million

0 1 2 3 4 5 6 7

On the number line, the whole number 36 is closer to 40 than 30, so 36 rounded
to the nearest ten is 40.

Farther Closer
36
30 35 40

The whole number 52 is closer to 50 than 60, so 52 rounded to the nearest ten is 50.

Closer Farther
52
50 55 60

In trying to round 25 to the nearest ten, we see that 25 is halfway between 20 and
30. It is not closer to either number. In such a case, we round to the larger ten, that
is, to 30.

Same Same
distance distance
25

20 25 30
Here, we round “up.”

To round a whole number without using a number line, follow these steps:

Rounding Whole Numbers to a Given Place Value
Step 1: Locate the digit to the right of the given place value.
Step 2: If this digit is 5 or greater, add 1 to the digit in the given place value and
replace each digit to its right by 0.
Step 3: If this digit is less than 5, replace it and each digit to its right by 0.

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