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Calculating area

Area is the amount of space taken up by a flat shape and is calculated by counting the square units inside it; almost like the tiles on a floor. For example, if we can repeatedly fit a square with 1cm sides inside a shape ten times perfectly, we can say that that shape has an area of 10 squared centimetres.

To make this simpler, and because Maths is such a universal language, we can also write this as 10����². This way, everyone, no matter what language they speak, will be able to recognise and understand this measurement.

The good news is, there is a much quicker way to calculate the area of basic shapes rather than counting the squares inside it.

For a rectangle or square, we can use the formula:

length x width (l x w) to find the area.

For example:

If a rectangle has a length of 6cm and a width of 4cm

Then the area would be 6cm x 4cm = 24cm²

However, the same formula cannot be applied to all shapes.

To find the area of a right angled triangle, you need to multiply the two perpendicular sides together and halve the result.

So, the area of a right angle triangle = ½ x b x h, where b is the length of the base and h is the perpendicular height of the triangle.

For example: ½ x 4cm x 4cm = ½ x 16cm = 8 squared centimetres or 8cm²

Compound shapes

On occasion, you may need to find the area of more irregular shapes, such as compound shapes. A compound, or composite, shape is made up of two or more basic shapes joined together. In this clip Prof Egg asks Trig to help him paint a wall with an unusual shape.

So by separating shapes back into their basic forms and using the correct formula to calculate the area of each, we can add these totals together to find the overall area of a compound shape.

Activity

Test your knowledge of calculating area with this quiz.