Teaching Models

Multiply Decimals

Multiplication of Decimals
To multiply a decimal by a whole number, multiply as if both numbers were whole numbers. Place the decimal point in the product so there are the same number of decimal places in the product as in the decimal factor.

Example:

2.18 times 6 equals 13.08

To multiply two decimals, multiply as if the numbers were whole numbers. To place the decimal point in the product, first count the total number of decimal places in the factors. Then place the decimal point that many places from the right in the product.

Example:

5.43 times 3.7 equals 20.091

The placement of the decimal point can be explained by using fractions.

3.7 times 5.43 equals 20.091

Multiplication of a decimal by 10 simply moves the decimal point one place to the right. Multiplication by 10n moves the decimal point n places to the right. Division by 10n moves the decimal point n places to the left.

Teaching Model 13.4: Multiply Decimals


Houghton Mifflin Math Grade 5