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Name the Triangle

In this worksheet, students work out the missing angle in a triangle in order to identify the type of triangle.

'Name the Triangle' worksheet

Key stage:  KS 3

Curriculum topic:   Geometry and Measures

Curriculum subtopic:   Apply Facts About Angles and Sides

Difficulty level:  

Worksheet Overview

Triangle Types

Remember that the interior angles of a triangle add up to 180º.

right-angled triangle has one 90º angle

An isosceles triangle has two equal angles

An equilateral triangle has three equal angles, each of size 60º


Two of the angles in a triangle are 34º and 112º.  Which type of triangle is it?



We must first work out the third angle which will be:

180º - (34º + 112º) = 180º - 146º = 34º


So the triangle has angles 34º, 112º, 34º 

Two angles are equal so it is isosceles.

Now, let's put these rules into practise...

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