Unit 9 Section 5 : The Area of a Triangle

This section introduces the formula for the area of a triangle, which can be seen below.

The height is called the perpendicular height because it is at a right-angle to the base.
Below is an example of the formula being used to find the area of a triangle.

Example Question

Below are two triangles, each with their base and perpendicular height indicated.
Practice Questions
Work out the answer to each of these questions then click on the button marked Click on this button below to see the correct answer to see whether you are correct.

What is the area of triangle A?

What is the area of triangle B?



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Question 1
Find the area of each of these triangles.
Part 1
(a) cm




(b) m




(c) cm




(d) mm




(e) cm



(f) cm



(g) cm




(h) mm

Question 2
Find the areas of the shapes below.
In each case, you will need to divide the shape into one rectangle and one triangle, then add the areas together.
Dashed lines have been included on each shape to help you with this.
(a) cm


(b) cm


(c) cm


(d) cm

You have now completed Unit 9 Section 5
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Produced by A.J. Reynolds January 2001