Rectangles and Squares

In a rectangle opposite sides are equal, so to work out the perimeter of a rectangle you just need to know the length and width.

Example 1

Here the length is 15 cm and the width 6 cm.

Method 1
Length = 15 cm and width = 6 cm
Perimeter = 15 + 6 + 15 + 6 = 42 cm

Method 2
Because opposite sides are equal you can also work out the perimeter in this way: double the length, double the width, then add the results together.
      (15 x 2) + (6 x 2) = 30 + 12 = 42

Method 3
Add the length and width then double it.
       15 + 6 = 21
       21 x 2 = 42

The method you choose is up to you - each one will give the same answer.

Example 2

A square is a rectangle with four equal length sides. So you only need to know the measurement of one side.
The perimeter of this shape can be worked out as
      5 + 5 + 5 + 5 = 20 m
Or you can multiply the length by four. 5 x 4 = 20