Classifying triangles

Learn about the different types of triangles and their properties.

This includes:

  • one video
  • a learning summary
  • one activity

Quiz

To get started, let's see how well you know this topic already. Take the quiz below to find out.

Learn

Triangles are a type of polygon (a 2D shape with straight lines).

There are four different types of triangles:

  • equilateral
  • isosceles
  • right-angled
  • scalene

Watch this video below from KS2 Maths to find out about the different types of triangles.

All triangles have three sides, but their sides and angles all change depending on what type of triangle you are looking at.

Let's take a look at the different types:

Equilateral

Equilateral triangles have three equal sides and three equal angles of 60°.

This is easy to remember because 'equilateral' sounds like 'equal'!

Isosceles

Isosceles triangles have two equal sides and two equal angles.

Right-angled

You can always spot a right-angled triangle because it has a right angle (90°).

The right-angle is usually marked by a small square in the corner.

Scalene

Scalene triangles have no equal sides and no equal angles.

Its sides and angles are all different sizes.

Let's take a look at some examples. How would you identify these triangles?

Example 1

To decide what type of triangle this is, you have to look at the properties of the shape.

Look at the length of the sides. Two sides are 5 cm and one is 8 cm.

Since two sides are the same length, this triangle must be an isosceles triangle.

Example 2

Look at the properties of the triangle - what are the measurements of the sides?

All sides are a different length, which makes this a scalene triangle.

Practise

Activity 1

Triangle machine

Try the activity below from KS2 Maths and label the types of triangle.

Play

Play Guardians: Defenders of Mathematica to learn more and sharpen your skills on this topic.

Guardians: Defenders of Mathematica

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