 # EdPlace's Year 4 Home Learning Maths Lesson: Geometric Shapes - Triangles

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Are they keen to start practising straight away? Head to the bottom of the page to find the activities.

Now...onto the lesson!

Key Stage 2 Statutory Requirements for Maths
Year 4 pupils should be able to compare and classify geometric shapes, including quadrilaterals and triangles, based on their properties and sizes.

# Geometric shapes and triangles

2D shape names are a key concept for children to learn by the end of Key Stage 2. There are 4 main types of triangle which can all appear similar, so it’s important that children are confident with the properties of each!

At EdPlace we’re surrounded by a team of experts who communicate these concepts with children on a day-to-day basis, and we’re ready to share their teaching gems with you.  Follow the step-by-step approach below to make naming triangles a breeze!

1) Understand what the properties of the main types of triangle are

2) Apply this understanding to naming and classifying triangles

3) Explain how shapes are similar and different by comparing them.

## Step 1 - Understand key terminology

Before we start exploring types of triangles, it’s important to check that your child understands what the key terminology means.

A triangle is a shape classified by having exactly 3 sides and 3 angles.

Sides make up the outline of the shape. In a triangle, they are always straight.
Angles are where sides meet and can be classified as acute (smaller than 90°), right angles (exactly 90° and marked with a square corner), obtuse (smaller than 180° but larger than 90°) or reflex (larger than 180°). Reflex angles are not found in triangles, so this is just for information. Angles in a triangle always add up to 180°.

## Step 2 - Check your child's prior understanding

In year 3, your child will have been taught to name a variety of different geometric shapes. They will have been taught how to classify shapes using properties including angles and sides. They will also have been introduced to the concept of different angles and should be able to name and recognise right, acute and obtuse angles.

In year 4, the concept of naming and classifying types of triangles is introduced and this can sometimes cause confusion for children as they have quite technical names and all have slightly different properties. To make things even more complicated, some triangles can be classified as more than one type! In the next section, we will explore how to ensure classifying triangles becomes nice and easy.

## Step 3 - Getting to grips with translation

In year 4, children will be taught to name, sort and classify types of triangles.

So, we’re going to look at some examples of the 4 main types and how to recognise them now before you try out some questions and activities.

Equilateral triangles – The name sounds a bit like equal doesn’t it! This is a good way to remember this type of triangle since all the angles are exactly that – equal!

Angles in a triangle always add up to 180°, so each angle in an equilateral triangle is 60°. Therefore, it has 3 acute angles. As you can see, these triangles also have 3 equal sides – this is shown on diagrams with 3 matching lines drawn onto the diagram. Isosceles triangles – These triangles have 2 equal angles and 2 equal sides. The angles are all acute, and when they are measured, they will yet again add up to 180°.

On the diagrams below, you can see the 2 equal sides are marked with straight lines across the sides and the 2 equal angles are marked by a double angle marker. Both are isosceles triangles, although they appear quite different!  Isosceles triangles can have a right angle, which would mean they also belong to a group called right-angled triangles. We will look at these next.

Right Angled Triangles – As the name suggests, this type of triangle is one which features a right angle. You can see in the diagram below, that right angles are often shown with a square corner. The angles still add up to 180° and the two other angles will always be acute, but not necessarily the same size. A right-angled triangle can be isosceles if one of its angles is 90°. Scalene Triangles – This final type of triangle has no equal sides or angles. Depending on the size of the angles, a scalene triangle can also be right angled! Can you spot the right-angled scalene triangle below? ## Step 4 - Putting it into practise...

Why not apply the above to the following triangles questions together?

a) Steve has drawn a triangle as follows. What type of triangle is it? b) Martha has a triangle with angles 70°, 10° and 100°. What type of triangle is it?

c) How many of these triangles could be labelled isosceles? d) Ben says he has drawn a triangle with 2 right angles. Is he correct? Explain why.

## Step 5 - Give it a go...

Now that you’ve covered this lesson together, why not put this to the test and assign your child the following geometry activities in this order? All activities are created by teachers and automatically marked. Plus, with an EdPlace subscription, we can automatically progress your child at a level that's right for them. Sending you progress reports along the way so you can track and measure progress, together - brilliant!

a) Steve has drawn a right-angled triangle. Due to the other angles being equal it could also be isosceles.

b) Martha has a scalene triangle.

c) There are 4 isosceles triangles. The other 2 triangles are right angled scalene and scalene.

d) A triangle can never have two right angles, so Ben is not correct. 2 angles of 90° would make a straight line, not a triangle!

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