Know that the perimeter is the distance around a 2D shape | Maths

Starter quiz

Which of these shapes has string around its outline?

a ✓

b

c
Which of these symbols means ‘greater than’?

<

> ✓

=
Which of these shapes are 2D shapes?
Is this a 2D shape? Select the best answer and reason.

Yes. It is a triangle.

No. It is a 3D shape.

No. It is not closed. ✓
Number rods have been used to make polygons. Which ones are polygons?

A ✓

B

C ✓
Which 2D shapes can you see on this football pitch?

Circle ✓

Semi-circle ✓

Square

Rectangle ✓

Hexagon

Exit quiz

Which of these is the definition of perimeter?

A straight line.

The distance around the outside of a 2D shape. ✓

The space inside a 2D shape.
Which of these are true of perimeter?

It does not matter if you go inside or outside the lines when finding perimeter.

You can start at any point in a shape, but you must finish at the same point. ✓

You must cover the whole of the outside of the shape. ✓

It does not matter if you go clockwise or anti-clockwise when finding perimeter. ✓
Which of these shows the perimeter of the triangle?

a

b ✓

c

d
In terms of perimeter, which of the statements are true of this image?

Shape A and B have equal perimeter.

The perimeter of Shape A is greater than Shape B.

The perimeter of Shape A is less than Shape B. ✓

The perimeter of Shape B is less than Shape A.

The perimeter of Shape B is greater than Shape A. ✓
In terms of perimeter, which of the statements are true of this image?

Shape A and B have equal perimeter.

The perimeter of Shape A is greater than Shape B. ✓

The perimeter of Shape A is less than Shape B.

The perimeter of Shape B is le less than Shape A. ✓

The perimeter of Shape B is greater than Shape A.
Order the shapes according to their perimeter, starting with the shortest perimeter.

1

⇔

d

2

⇔

a

3

⇔

b

4

⇔

c

Worksheet

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Presentation

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Video

Lesson Details

Key learning points

Perimeter is a measurement of length.
Perimeter is the distance around a 2D shape.

Common misconception

When finding the perimeter of a shape, pupils may count one side twice, or not count one of the sides.

Examples and non-examples of perimeter are given but encourage pupils to mark a 'start point' when they find the perimeter of a shape, so that they know where to end.

Keywords

Perimeter - The distance around a 2D shape.