2-dimensional shapes are flat. The perimeter of a 2D shape is the total distance around the outside of the shape. The area of a 2D shape is the space inside the shape.

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The **perimeter** is the total distance around the edge of a 2D shape. Examples of units of distance are millimetres (mm), centimetres (cm) and metres (m).

A fence is built around the perimeter of a field. What is the total length of the fence?

The perimeter of any 2D shape can be found by labelling and adding together each side.

Remember to include the length of each side when calculating the perimeter.

- Question
What is the perimeter of an equilateral triangle, when the length of one side is 4 cm?

An equilateral triangle has three sides of equal length. The perimeter of the equilateral triangle is

A compound shape is made up of several simple 2D shapes. To calculate the perimeter, label and add up the length of each side.

What is the perimeter of this shape?

First, calculate the missing lengths and .

Second, label each length.

Add up all the sides to calculate the perimeter.

Remember to make sure that all the sides have been included.