Perimeter · Year 4
In Year 4 you learn: perimeter of rectilinear shapes.
The perimeter of a shape is the distance all the way round it: add the lengths of all its sides. For a rectangle, perimeter = 2 × (length + width). Perimeter is a length, so it is measured in cm, m or km.
Key facts
- Perimeter is the distance all the way round a shape: add up all its sides.
- A square has 4 equal sides, so its perimeter is 4 × the side.
- Rectilinear shapes: work out any missing sides from the others first.
Worked examples
Example 1
Find the perimeter of a rectangle 6 cm long and 4 cm wide.
Answer: 20 cm
Example 2
A triangle has sides of 5 cm, 7 cm and 8 cm. What is its perimeter?
Answer: 20 cm
Example 3
A square has sides of 9 cm. What is its perimeter?
Answer: 36 cm
Example 4
Find the perimeter of this L-shape. All corners are right angles; lengths are in cm.
Answer: 34 cm