Multiplying decimals

Multiplying decimals

Previously, we learned how to add and subtract decimal numbers. In this section, we will learn how to multiply decimal numbers. As learned in previous section, when adding and subtracting decimal numbers, the decimal points must be lined up. In contrast, when multiplying decimal numbers, it is not important that the decimal points be lined up. Instead, it is important to line up the digits in the lowest place values of both numbers. In order to figure out where to place the decimal point in the answer, we must count how many digits total, between the two numbers being multiplied together, are behind the decimal points.

Lessons

• Introduction
a)
How to multiply decimals?

b)
How to round decimals?

• 1.
Complete each multiplication statement.
a)
0.57 x 100 =

b)
5.43 x 0.1 =

c)
8.71 x 3.6 =

d)
32.8 x 0.02 =

• 2.
Hannah's favorite soft drink is coke. Her mother gives her $4.50 to spend on coke one afternoon. She goes to the local grocery store and buys four bottles of coke. Each bottle costs$1.05. Does she have enough money to make this purchase?

• 3.
Every Saturday morning Alan's bakery sells cinnamon buns for a special price of \$2.50. If Barb's two sisters go to the bakery every Saturday morning for two years, how much will they spend? Assume they each purchase one bun per visit. Round your answer to the nearest hundredth.