Lesson 2 – Multiplying Decimals By 10 & Multiples Of 10

Objective:

At the end of this lesson, students should be able to multiply decimals by 10 and multiples of 10.

Decimals are numbers that have a decimal point in between two digits in the number. When decimals are multiplied by multiples of 10, the position of the digit moves a step /steps to the left depending on the number of zeros making it look as though the decimal point has shifted one place or more to the right according to the number of zeros multiplying the decimal number.

Example 1

127.8 x 10 = 1278

From the example above, we observe that, the place value of the 8 has changed from 8 tenths to 8 units.

Example 2

23.567 x 100

Solution

The decimal number is multiplied by 100, which has two zeros so all the digits change their place value, moving two steps from right to left. The number becomes 100 times bigger.

The place value of the 2 has changed from ten to thousand. The value of the 3 has changed from 3 units to 3 hundreds. The value of the 5 has changed from 5/10 to 50. Also the value of the 6 has changed from 6 hundredths to 6 units, while the value of the 7 has changed from 7/1000 to 7/10. These movements make it look like the decimal point moved two steps to the right side giving us the answer 2356.7.

Example 3

743.9 x 1000 =743900

Here the value of all the digits has become 1000 times bigger. The value of the 9 has changed from 9/10 to 900.

Example 4

0.005 x 10 =0.05