Calculate Areas of Rectangles

In this activity, we are going to be calculating the area and perimeter of rectangles using the information provided.

The area of a rectangle is its length x width  (l x w).

The perimeter of a shape is the total distance around the edge.

Area is calculated in m²  or cm² 

Perimeter is usually measured in m or cm 

Let's have a look at an example.

Here is a rectangle (not to scale):

If the area is 200 m² and the width is 20 m, what is the perimeter?

We can work out the area using this information.

We know the width is 20 m

We know the area is 200 m²

We know that area is l x w (a = l x w)

We can divide the area by the width to find the length (a ÷ w = l)

200 ÷ 20 = 10

The length is 10 m

The perimeter will be 20 + 20 + 10 + 10 = 60 m

We can check this by multiplying 20 by 10 = 200 

Top Tip:  Read the information in each question carefully and use it to work out the answer.  It can help to draw out the shape on paper.