Page 312 - Basic College Mathematics with Early Integers

4.2 ADDING AND SUBTRACTING DECIMALS Objectives

Add Decimals.
Objective Adding Decimals Subtract Decimals.

Adding decimals is similar to adding whole numbers. We add digits in correspond- Estimate when Adding or
ing place values from right to left, carrying if necessary. To make sure that digits in Subtracting Decimals.
corresponding place values are added, we line up the decimal points vertically.
As we shall see later in this section, subtracting decimals is similar to subtract- Evaluate Expressions with
ing whole numbers, also. Decimal Replacement Values.

Solve Problems That Involve
Adding or Subtracting Decimals.
Adding (or Subtracting) Decimals
Step 1: Write the decimals so that the decimal points line up vertically.

Step 2: Add or subtract as with whole numbers.
Step 3: Place the decimal point in the sum or difference so that it lines up ver-
tically with the decimal points in the problem.

In this section, we will insert zeros in decimal numbers so that place value digits line
up neatly.This is shown in Example 1.

Example 1 Add: 23.85 + 1.604 PRACTICE 1
Add.
Solution: First we line up the decimal points vertically.
a. 15.52 + 2.371
23.850 Insert one 0 so that digits line up neatly. b. 20.06 + 17.612
+ 1.604 c. 0.125 + 122.8
c
Line up decimal points.
Then we add the digits from right to left as for whole numbers.

1
23.850
+ 1.604
25.454
Place the decimal point in the sum so that all decimal points line up.
Work Practice 1

Recall that 0s may be placed after the last digit to the right of the decimal point
without changing the value of the decimal.This may be used to help line up place
values when adding decimals.

3.2 becomes 3.200 Insert two 0s.
15.567 15.567
+ 0.11 + 0.110 Insert one 0.
18.877 Add.
Answers
1. a. 17.891 b. 37.672 c. 122.925

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