Multiply Decimals

In this activity, we will be multiplying decimal numbers.

 

 

The easiest way to do this is to remove the decimal point from the numbers, multiply them together and then put the decimal point back in again.

 

We need to count how many numbers there are after the decimal point and make sure that there are the same number after the decimal point in the answer.

 

Example 1

 

7.35 × 31 

There are two numbers after the decimal point.

Remove the decimal point and do the calculation 735 x 31

735 x 31 = 22785

 

Finally, put the decimal point back in. There must be the same number of decimal places in the answer as there were in the original calculation, so that is two.

 

 So, 7.35 x 31 = 227.85

 

Example 2

2.7 × 0.412

Count the numbers after the decimal point. There are four.

Remove the decimal point and do the calculation 27 x 412

412 x 27 = 11124

 

Finally, add the decimal point back in, making sure that we still have four decimal places: 1.1124

2.7 x 0.412 = 1.1124

 

Let's have a go at some questions now.