Sort 2D and 3D shapes - KS2 Maths - Year 3

What are 2D shapes?

Two-dimensional (2D) shapes are completely flat. They cannot be picked up.

A polygon is a 2D shape with straight sides that meet at vertices.

Polygons have names that show the number of sides they have.

A three-dimensional (3D) shape is a solid shape.

3D shapes have three dimensions - length, width and depth.

Look at the shapes of the faces to help recognise these 3D shapes.

3D shapes can have flat or curved faces.

Why not see how much you know about this topic already? Then work through the page and see if you can beat your score.

Polygons have different properties that you can use to classify them. This includes:

Regular polygons are shapes where the lengths of the sides and the inside angles are equal.

Irregular polygons are shapes where the sides and inside angles are not equal.

Have a look at these two shapes. How are these the same? How are they different?

They both have four sides.

However, when you compare the properties, the length of the sides is the difference.

A square is a regular polygon. It has sides of equal length and equal angles.

A rectangle is an irregular polygon. It has equal angles, but the sides are not all equal in length.

Now look at these triangles. How are they the same? How are they different?

They all have the same number of sides and vertices.

However, look closely at the length of the sides and the angles.

Only the orange triangle has 3 equal sides and 3 equal angles.

This is a regular polygon. It is called an equilateral triangle.

The other triangles are irregular polygons.

A 3D shape is a solid shape. 3D shapes have three dimensions:

3D shapes have different properties to 2D shapes.

Faces - A face is a flat surface on a 3D shape.

Edges - An edge is where two faces meet. For example a cube has 12 edges.

Vertices - A vertex is a corner where edges meet. The plural is vertices.

For example, this cuboid above 6 faces, 12 edges and 8 vertices.

The table below shows how the faces of some other 3D shapes compare.

To sort shapes, you can compare different properties. Carroll diagrams and Venn diagrams can be used to sort shapes.

Image caption,
Look at these 6 shapes. Let's sort them using a Carroll diagram and a Venn diagram
Image caption,
Carroll diagram
A Carroll diagram is a table that can be used to group shapes according to their properties. Look at how these shapes have been sorted. Remember a quadrilateral is any shape with 4 straight sides.
Image caption,
Venn diagram
Now the shapes have been sorted using a Venn diagram. What is special about the square? It is a quadrilateral and a regular shape. Can you guess why the right-angled triangle in the outside set? It is not a quadrilateral or a regular shape.