Similar shapes

When a shape is enlarged, the image is similar to the original shape. It is the same shape but a different size.

These two shapes are similar as they are both rectangles but one is an enlargement of the other.

Similar triangles

Two triangles are similar if the angles are the same size or the corresponding sides are in the same ratio. Either of these conditions will prove two triangles are similar.

Triangle B is an enlargement of triangle A by a scale factor of 2. Each length in triangle B is twice as long as in triangle A.

The two triangles are similar.

Example 1

State whether the two triangles are similar. Give…