In this activity, we will multiply numbers by 0.1 and 0.01.

When you multiply by 0.1, you are simply dividing by 10.

When you multiply by 0.01, you are simply dividing by 100.

**Examples**

15.1 × 0.1 = 15.1 ÷ 10 = 1.51

0.123 × 0.01 = 0.123 ÷ 100 = 0.00123

When multiplying with decimal numbers, we need to count how many **decimal places **we have in our calculation and make sure that we have the** same** **number **in our answer!

In the first example above, we have **two decimal places** in the calculation: 15.__1 __x 0.__1__, so our answer must have two decimal places: **1. 51**

In the second example, we have **five decimal places** in the calculation: 0.__123__ x 0.__01__, so our answer must have five decimal places: **0. 00123**

If you remember this rule about decimal places, you'll find multiplying decimals becomes really simple.

Let's have a go at some questions now.