Class 4 Maths — Perimeter: once round the outside

Find the perimeter of any straight-sided shape by adding the lengths of its sides, and work backwards to a missing side.

Name: ________________________

Before you start

An L-shaped garden, with every side drawn as its own strip. Find all of them, and count how many there are.

Six sides, not four — the step in the middle adds two more, and leaving one of those out is the commonest way a perimeter goes wrong.

1.A regular octagon has a perimeter of 56 cm. How long is each side, in centimetres? Give just the number.
2.A rectangle is 12 cm long and 7 cm wide. What is its perimeter, in centimetres? Give just the number.
3.Every length here is in centimetres. Which shape has the largest perimeter?
- a) A square of side 6
- b) A regular pentagon of side 5
- c) A triangle with sides 7, 7 and 7
- d) A rectangle 8 by 3
4.A triangle has sides of 6 cm, 8 cm and 5 cm. What is its perimeter, in centimetres? Give just the number.
5.Every side of every shape here is 6 centimetres long. Match each regular shape to its perimeter.
- Triangle
- Square
- Pentagon
- Hexagon
- Octagon
- 30
- 18
- 36
- 24
- 48
6.A four-sided shape has sides of 3 cm, 7 cm, 4 cm and 9 cm. What is its perimeter, in centimetres? Give just the number.
7.A square has a perimeter of 32 cm. How long is each side, in centimetres? Give just the number.
8.A path goes right round a rectangular lawn 15 m long and 10 m wide. How far is it once round, in metres? Give just the number.