Multiplication as scaling

When you want to describe the size of an object compared to a smaller object, you can use the word ‘times’.

For example, you can say an object is 'five times' as large or 'ten times' as large.

This will depend on how much you have multiplied the original size by.

This blue tower is three times the height of the orange tower.

Test out your knowledge of scaling with this quiz, then read on to complete the page.

Here are some pencils.

There is one yellow pencil and there are three blue pencils.

The blue pencils are all the same length.

You know the length of the blue pencils, but how can you work out the length of the yellow pencil?

You can work it out using multiplication.

4cm multiplied by 3 is 12cm.

4cm × 3 = 12cm

The yellow pencil is 12cm long. It is three times the length of a blue pencil.

Now look at these pencils.

The yellow pencil is double the length of a green pencil. You could also say it is two times, or twice as long.

How long is the green pencil?

You can work it out using division.

12cm divided by 2 is 6cm.

12cm ÷ 2 = 6cm

The green pencils are 6cm long.

You can write this as a multiplication like this:

2 × 6cm = 12cm

Using multiplication for comparing height

This picture shows how much a plant has grown over time.

When it was planted, it was 10cm tall. How can you work out how tall it is now?

The plant has grown ten times taller. Its original height was 10cm.

10 × 10cm = 100cm

The plant is now 100cm.

Using multiplication to compare time

Sally has taken 5 minutes to eat her lunch. Fred has taken four times as long to eat lunch.

How can you work out how long he took?

You need to multiply 5 minutes by 4.

5 minutes × 4 = 20 minutes

Fred has taken 20 minutes to eat his lunch.