For a rectangle, area = length × width and perimeter = 2 × (length + width). Area tells us how much surface is covered, so it uses square units like cm². Perimeter is a distance, so it uses cm.
You can work backwards. If a rectangle has an area of 48 cm² and a width of 6 cm, its length is 48 ÷ 6 = 8 cm. If a rectangle has a perimeter of 30 cm and a length of 9 cm, its width is 15 − 9 = 6 cm.
Worked example
A garden is 12 m long and 7 m wide. What is its area?
- Area = length × width.
- 12 × 7 = 84.
Answer:84 m²
Key words
- area
- the surface a shape covers
- perimeter
- the distance around a shape
- formula
- a rule written with words or letters
Practise this
New questions every time.
Common Core-referenced: 4.MD.A.3