Lesson 4 — Activity 3: Multiplying and Dividing Decimal Numbers


Getting Ready


Now think back to the activities you completed on multiplying and dividing whole numbers (L3 — A2 and A3).

You will follow the same processes for multiplying and dividing decimal numbers.

The one major difference is that you must remember the decimal point!

This image shows an example of division with decimal numbers.
Image courtesy of www.imagesgoogle.com

As with multiplying and dividing whole numbers, many strategies can be used to solve multiplying and dividing decimal numbers, such as using:
 
  • base 10 blocks (manipulatives) Base ten blocks are used to solve many math problems.


  • estimating and calculating by using paper and pencil


  • checking, by using a calculator 


Click here to watch a video that demonstrates multiplying and dividing decimal numbers.



The video explained in some detail about making estimates before calculating.


Here's some further information regarding this:


Use rounding to estimate how much 12.70 × 6.24 is.
  • 12.70 rounds to the whole number 13.
  • 6.24 rounds to the whole number 6.

Multiply 13 × 6 to provide an estimated answer.


13 × 6 = 78


OR


Round to multiples of 10 and then multiply.
  • 12 rounds to 10.
  • 6 rounds to 10.


10 × 10 = 100.

(The correct answer is 12.70 × 5.24 = 79.2.)



Click here to try for some extra practice on multiplying and dividing decimals. Answers are provided for you.