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Practise Calculating the Area of Triangles

In this worksheet, students will calculate the areas of triangles.

'Practise Calculating the Area of Triangles' worksheet

Key stage:  KS 2

Year:  Year 6 Maths worksheets

Curriculum topic:   Measurement

Curriculum subtopic:   Calculate Areas

Difficulty level:  

Worksheet Overview

We use the following formula to work out the area of a rectangle:

 

Rectangle area

 

We need to know the base length and the perpendicular height from the base to the top.

 

Area of rectangle = base × height (b x h)

 

Let's have a go:

 

What is the area of a rectangle with the following measurements?

Base = 9 cm

Height = 7 cm

9 cm x 7 cm = 63 cm²

 

boy with football

 

We can use this formula to work out the area of a triangle.

 

Try this with a piece of paper.

Start with a rectangle.

 

Rectangle

 

Cut off a right-angled triangle from the left-hand side and separate the two pieces.

The area of the two pieces together will be the same as the original rectangle.

 

Cut right-angled triangle from left-hand side of rectangle

 

Cut off a right-angled triangle from the right-hand side to form a triangle in the middle, and separate the three pieces.

The area of the three pieces will still be the same as the original rectangle.

 

Cut right-angled triangle from the middle of paper

 

Now look carefully at the pieces marked A and B below.

Notice that the areas match. 

A matches A and B matches B.

 

Matching triangles from rectangle

 

So, the area of the triangle in the middle is half the area of the rectangle.

 

Area of Triangles

 

Area of triangle

 

We need to know the base length and the perpendicular height from the base to the apex. (not the slant height)

 

Area of triangle = ½ base × height

or

Area of triangle = base × height ÷ 2

 

 

Example

Calculate the area of this triangle in cm2

 

Area of triangle

 

Answer

If we turn our heads to the left, the base length is 12 cm and the perpendicular height is 6 cm.

We do not need to know the slant height of 10 cm to use the formula.

 

Area of triangle = ½ base × height

Area = ½ × 12 × 6 = 6 × 6  =  36 cm2

or

Area of triangle = base × height ÷ 2

Area = 12 x 6 ÷ 2 = 72 ÷ 2 = 36 cm2

 

Now, why don't you have a go at calculating the area of some triangles?

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