Basic Mathematics for College Students

332 Chapter 4 Decimals

Carry a 2 (shown in blue) to the ones column.

Carry a 2 (shown in green) to the tens column.

Write the decimal point in the result directly

below the decimal points in the addends.

The sum is 122.293.

31

2

.913

5.600

68.000

 16.780

122.293

Success Tip In Example 1, the digits in each place-value column were added

from top to bottom.To check the answer, we can instead add from bottom to

top.Adding down or adding up should give the same result. If it does not, an

error has been made and you should re-add.

To check,

add

bottom

to top

122.293

31.913

5.600

68.000

 16.780

122.293

First add

top to

bottom

Using Your CALCULATOR Adding Decimals

The bar graph on the

right shows the number

of grams of fiber in a

standard serving of

each of several foods. It

is believed that men can

significantly cut their

risk of heart attack by

eating at least 25 grams

of fiber a day. Does this

diet meet or exceed the

25-gram requirement?

To find the total fiber intake, we add the fiber content of each of the foods. We

can use a calculator to add the decimals.

3.1 12.75 .9 3.5 1.1 7.3

On some calculators, the key is pressed to find the sum.

Since 28.65 25, this diet exceeds the daily fiber requirement of 25 grams.

ENTER

      28.65

15

10

5

3.1

0.9

3.5

1.1

7.3

12.75

Grams of fiber

1

Grapefruit

Bran

cereal

Lettuce 1

Apple

Spaghetti Kidney

beans

2 Subtract decimals.

Subtracting decimals is similar to subtracting whole numbers. We use vertical form

and stack the decimals with their corresponding place values and decimal points lined

up so that we subtract similar objects—hundredths from hundredths, tenths from

tenths, ones from ones, and so on. We write the decimal point in the differenceso that

2