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How to calculate the area of a triangle

This is the complimentary worksheet for this tutorial. Below are four different exercises for you to work

through, followed by the worked-through solutions.

Exercise 1.

A. What is the area of the triangle below?

B. For extra points, what type of triangle is it?

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Exercise 2.

A. What is the area of the triangle below?

B. For extra points, what type of triangle is it?

Exercise 3.

A. What is the area of the triangle below?

B. For extra points, what type of triangle is it?

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Exercise 4.

A. What is the area of the triangle below?

B. For extra points, what type of triangle is it?

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Answers

Exercise 1.

A: area = (width x height) ÷ 2

= ( 4 x 4 ) ÷ 2

= 16 ÷ 2

= 8 square units

B: It's an isosceles triangle because two sides of the triangle are equal, and the angles opposite those

sides are also equal.

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Exercise 2.

A: area = (width x height) ÷ 2

= ( 4 x 6 ) ÷ 2

= 24 ÷ 2

= 12 square units

B: It's a scalene triangle because all three sides and angles are different.

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Exercise 3.

A: Either you need to use a ruler to measure the width and height, or you need to turn the triangle

around so that you can use the 'graph paper' background to count squares. We have done the second

(as you can see in the image below).

area = (width x height) ÷ 2

= ( 5 x 8.25 ) ÷ 2

= 41.25 ÷ 2

= 20.6 square units

B: It's a scalene triangle because all three sides are different. They look similar, and they almost are - but

the right side is slightly longer than the left.

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Exercise 4

A: area = (width x height) ÷ 2

= ( 6 x 7 ) ÷ 2

= 42 ÷ 2

= 21 square units

B: It's a right-angled triangle because it has a right angle (90 degree angle). It can also be described as a

scalene triangle because the sides are all of different lengths.