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Find the Area of a Triangle

In this worksheet, students will learn the formula for finding the area of a triangle and use it to calculate areas.

'Find the Area of a Triangle' worksheet

Key stage:  KS 4

GCSE Subjects:   Maths

GCSE Boards:   AQA, Eduqas, Pearson Edexcel, OCR,

Curriculum topic:   Geometry and Measures, Mensuration

Curriculum subtopic:   Mensuration and Calculation Area Calculations

Difficulty level:  

Worksheet Overview

Did you play one of these at school when you were younger?

 

A triangle

 

The good old days of the triangle before they became bothersome in maths questions.

 

What examples can you think of that we see in everyday life?

 

roof

 

Builders may need to know about triangles for working out the areas of gable ends of houses.

You might need to know the area for cutting patterns in the shape of a triangle to make bunting, or make a kite.

Before we can do any of these, there is one thing we need to know, and that is how to find the area of a triangle.

 

First, we are going back to look at how to find the area of a square and rectangle.  Why?  It might help you to understand and remember the formula for the area of a triangle.

 

A red rectangle

 

Area of a rectangle = base x height

 

A green rectangle divided into triangles

 

In the diagram above, look what happens when a diagonal line is drawn from one corner of the rectangle to the other.  By cutting it in half, I have made two triangles. Cutting it in half is the same as dividing by 2.

 

The area of each half, or each triangle = base x height ÷ 2

or another way of writing this is:

Area = 1/2 base x height

 

a dog

 

Now you could go barking up the wrong tree, so be careful!

When you are given measurements for a triangle, you are sometimes given the base, vertical height and a slanted height.  

You always want the vertical height.

 

Triangle

 

To find the area of this triangle we need to know the base of 4 x vertical height of 3 = 12

12 ÷ 2 = 6 units²  

 

Once you have learned the formula you are flying!

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