Multiply decimals by 10, 100, 1000 - Maths - Learning with BBC Bitesize - BBC Bitesize (2024)

Multiplying decimals helps you in everyday life. It can be used to:

• convert pounds into pence
• convert measures, such as kilograms to grams and millilitres to litres
• convert length, for example if you needed to work out how many metres were in centimetres

You can use place value charts to help multiply by 10, 100 and 1000. This helps you to see how the digits increase in value.

A trick to help you remember how many places the digits need to move is by looking at the zeros in 10, 100 and 1000.

For example, there are 3 zeros in 1000, so you need to move the digits 3 places to the left to multiply by 1000.

• x10 - 1 zero move 1 place
• x100 - 2 zeros move 2 places
• x1000 - 3 zeros move 3 places

To multiply by 10, you move the digits one place value to the left.

Let's look at an example:

4.2 x 10 = 42

Look at the slideshow below to see how the place value of each digit changes when you multiply by 10.

To multiply by 100, you move the digits two places to the left.

3.12 x 100 = 312

To multiply by 1000, you move the digits three place value places to the left.

0.04 × 1000 = 40

Do you notice in the example above there is now a zero in the ones column? This is to represent that the answer has no ones after the digits have increased in place value.

If you didn’t include the zero in the ones column, the answer would be very different since the value of the digits are completely wrong - 0.04 × 1000 is not 4!

This shows how important it is to understand place value when multiplying by 10, 100 or 1000 and why using a chart can be very handy.

Ask your parent or guardian to give you a small handful of coins, or draw some coins on small squares of paper.

Count how much money you have altogether and write it down, including a decimal place.

For example, one pound fifty would be:£1.50.

If you have got less than a pound it should look something like this:46p = £0.46.

Next, use some of the techniques you have learned in this guide to answer the following:

• How much would you have if you had ten times as much money?

• How much would you have if you had one hundred times as much money?

• How much would you have if you had one thousand times as much money?