measurement · Year 4 · AC9M4M02
Perimeter of a rectangle
The perimeter is the total distance all the way around the outside of a shape. A rectangle has two lengths and two widths, so add all four sides. For a 5 cm by 3 cm rectangle: 5 + 3 + 5 + 3 = 16 cm, which is the same as 2 × (5 + 3). Only two measurements are printed, but each one is used twice. Multiplying the two sides together gives the area instead, not the perimeter.
Sample questions
A rectangle is 6 cm long and 5 cm wide. What is its perimeter (in cm)?
- Perimeter is the distance around all four sides: 6 + 5 + 6 + 5.
- P = 2 × (6 + 5) = 2 × 11 = 22 cm.
Answer: 22
A rectangle is 4 cm long and 3 cm wide. What is its perimeter (in cm)?
- Perimeter is the distance around all four sides: 4 + 3 + 4 + 3.
- P = 2 × (4 + 3) = 2 × 7 = 14 cm.
Answer: 14
A rectangle is 7 cm long and 3 cm wide. What is its perimeter (in cm)?
- Perimeter is the distance around all four sides: 7 + 3 + 7 + 3.
- P = 2 × (7 + 3) = 2 × 10 = 20 cm.
Answer: 20