Multiply Decimal Numbers by One-Digit Numbers

In this activity, we will learn how to multiply a decimal number by a single digit number.

Example

Work out 3.87 × 7

Answer

If we multiply 3.87 by 100, we get 387.

Now work out 387 × 7 = 2709

Then divide 2709 by 100 to 'cancel out' the fact that we multiplied by 100 earlier. 

This gives the answer 2709 ÷ 100 = 27.09

Does that make sense?

We can always check our answers by counting how many numbers after the decimal point we have - that is, how many decimal places we have.

There should always be the same number of decimal places in the answer as there are in the calculation.

In our question, 3.87 had two decimal places, so there must be two decimal places in our answer, which there are! 27.09 has two decimal places!

Ready to try some questions?