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A scale factor is when you enlarge a shape and each side is multiplied by the same number. This number is called the scale factor.

Maps use scale factors to represent the distance between two places accurately. Without the scale, the map would just be a drawing.

Scale factors are also used by architects when they are drawing plans for a new house or building. The scale factor lets the constructors know the accurate length and height of what they are building. Watch this video to find out more.

Look at these two shapes.

If A is the original shape, what has happened to each side to create B?

Each side has doubled in length so it has been multiplied by 2. This means A has been enlarged by a scale factor of 2.

What is the scale factor of enlargement from shape A to B?

Look at the relationship between the two measurements.

Use your times tables knowledge - what do you multiply 3 by to get 33?

3 cm x ___ = 33 cm

You multiply by 11!

The scale factor is 11.

You can also use scale factors to find out the original measurement of a shape. Just use the inverse of multiplication, which is division.

You can also use scale factors to find out the original measurement of a shape. Just use the inverse of multiplication, which is division.

Work out the original length of a side that had been enlarged by a scale factor of 7.

You already know what the result of the enlargement is (49 cm) and that the scale factor is 7.

Remember, when enlarging a shape, you multiply the original length by the scale factor:

original length x 7 = 49 cm

You can work backwards and use the inverse operation which is division:

49 ÷ 7 = 7 cm

The original size of the length before enlargement is 7 cm.

Practise using scale factors in this quiz. If you have a printer at home, here's some you can download to help with today's activity.

See if you can put what you learned about scale factor to the test with this quiz.