Use the Perimeter to Find the Length of One Side

This activity is about finding the perimeter of regular 2D shapes. A regular shape is a polygon with sides that are all equal in length.

The perimeter is the total distance around the outside of a 2D shape. We can calculate the perimeter by adding together all the lengths of the sides.

Example

What is the length of one side?

Perimeter: 70 cm

Answer

First, count the number of sides.

There are 10 in this regular shape. It is a decagon.

If the length of 10 equal sides adds to 70 cm, we can divide to find the length of one side.

70 ÷ 10 = 7

Each side is 7 cm long.

Remember to put cm in the answer.

Let's have a go at some questions now.