Similarity in mathematics has a precise meaning, unlike its usage in everyday life. 2 shapes are said to be similar if they fulfill the following 2 conditions:

  1. The corresponding angles on the 2 shapes are equal
  2. One shape is an enlargement of the other shape by a scale factor

Let’s start with a simple example to demonstrate these 2 conditions.


With similar shapes you can be asked 2 type of questions.

  1. Find the scale factor given two similar shapes
  2. Find a missing side given two similar shapes

Finding the Scale Factor

To find the scale factor of two similar shapes, do the following:

  • Take two corresponding sides and divide the larger one by the smaller one.

Finding a missing side

To find a missing side, we need to know the scale factor a shape has been increased (or decreased) by. Here is how it is done.

Nth Term of a Quadratic Sequence
Best Fit on a Scatter Diagram