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Shapes are similar if all the sides are in the same ratio.

This means that shapes are similar if one is an enlargement of the other!

This is not the same as another tricky maths word - congruent. Two shapes are congruent if they are exactly the same! Same sides, same angles, same everything!

In questions about similar shapes you are most likely to be asked to find a missing side when you are given two similar scale factor.

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So, for the example below:

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which is 1.5 so to find x we multiply 5.8 by 1.5 giving x = 8.7cm.



1. Always make sure that the shapes are drawn the same way round. If they're not then redraw them.

2. Always use corresponding sides when you work out the scale factor.

3. Don't forget that in enlargements the angles don't change!

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