Similar Triangles

Free interactive math game: Similar Triangles — Find missing side. Part of the Geometric Shapes category on MathKite.

Example problems

Taken from the generator that powers this exercise. A fresh set appears every time the page is opened, and the printable worksheet holds ten of them.

  1. Two similar triangles. Small sides: 3, 4, 5 Large sides: ?, 16, 20 Find the missing side.
  2. Two similar triangles. Small sides: 3, 4, 5 Large sides: 6, 8, ? Find the missing side.
  3. Two similar triangles. Small sides: 3, 4, 5 Large sides: ?, 8, 10 Find the missing side.
  4. Two similar triangles. Small sides: 3, 4, 5 Large sides: ?, 20, 25 Find the missing side.

About this exercise

Triangles of the same shape but different size.

How to solve it

Corresponding sides share a single scale factor. Find it from a matching pair, then apply it to the side you need.

Worked example

If sides of 3 and 6 correspond, the factor is 2, so a side of 5 becomes 10.

Common mistake

Pairing the wrong sides. Corresponding sides sit opposite equal angles.