# Lesson 12- Multiplying Decimals By 10, 100 Or 1000

Objective

At the end of this lesson, students should be able to multiply decimal numbers by 10, 100 or 1000.

Decimals can easily be multiplied by 10, 100 and 1000.

• Anytime a decimal is multiplied by 10, each digit of the decimal moves 1 place to the left.

Example 1

a) 1.24 x 10    b.  13.5 x 10    c.  15.0 x 10

Solution

a) Move the digits the required number of times and fill the empty places with zero(s)  NB: Every decimal ending with point zero (.0) is a whole number.

• When a decimal number is multiplied by 100, each of the decimal moves 2 places to the left

Example 2

a) 4.86 x 100    b.  15.5 x 100

Solution

Move each digit 2 places to the left and fill empty spaces with zeros. • When a decimal is multiplied by 1000, each digit of the decimal moves 3 places to the left.

Example 3

a) 4.273 x 1000    b.  0.6 x 1000

Solution

Move each digit 3 places to the left and fill the empty spaces with zeros. (Note that we do not write ‘0’ in the thousandth place in the answer because we can’t start a number with a zero)

Unit 10 Lesson 12: Exercise 1

Complete the following multiplications: 1) 182.4   2) 3685   3) 186.4   4) 13124.8   5) 9763.1
6) 28.4   7) 8   8) 240   9) 3978.2   10) 7.3

Unit 10 Lesson 12: Exercise 2

Provide the correct answers for the following 1. 0.86   2. 13.58   3. 648.9   4. 8723
5. 7.6   6. 0.8   7. 43   8. 720
9. 1005   9. 1040   11. 0.06   12. 16400

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