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Year 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.

123456
  1. 1. The top side
  2. 2. The short side going down
  3. 3. The step across
  4. 4. The long side going down
  5. 5. The bottom side
  6. 6. The tall side up the left

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. 1.A square has a perimeter of 32 cm. How long is each side, in centimetres? Give just the number.

  2. 2.A regular octagon has a perimeter of 56 cm. How long is each side, in centimetres? Give just the number.

  3. 3.A rectangle is 12 cm long and 7 cm wide. What is its perimeter, in centimetres? Give just the number.

  4. 4.Every length here is in centimetres. Which shape has the largest perimeter?

    • a) A regular pentagon of side 5
    • b) A triangle with sides 7, 7 and 7
    • c) A square of side 6
    • d) A rectangle 8 by 3

  5. 5.Every length here is in centimetres. Put these shapes in order by perimeter, smallest first.

    • A square of side 4
    • A square of side 8
    • A rectangle 5 by 4
    • A regular hexagon of side 4
    • A square of side 3

  6. 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. 7.Every length here is in centimetres. Sort each shape by whether its perimeter is below 30 or above 30.

    Groups: Perimeter below 30 · Perimeter above 30

    • A triangle with sides 8, 9 and 10
    • A rectangle 9 by 7
    • A square of side 6
    • A regular hexagon of side 6
    • A rectangle 10 by 4
    • A regular pentagon of side 7

  8. 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.

Answer key — Year 4 Maths — Perimeter: once round the outside

  1. 1. 8
  2. 2. 7
  3. 3. 38
  4. 4. a) A regular pentagon of side 5
  5. 5. 1. A square of side 3 2. A square of side 4 3. A rectangle 5 by 4 4. A regular hexagon of side 4 5. A square of side 8
  6. 6. 23
  7. 7. A square of side 6 → Perimeter below 30; A rectangle 10 by 4 → Perimeter below 30; A rectangle 9 by 7 → Perimeter above 30; A regular pentagon of side 7 → Perimeter above 30; A triangle with sides 8, 9 and 10 → Perimeter below 30; A regular hexagon of side 6 → Perimeter above 30
  8. 8. 50