Practice Area of rectangles
A rectangle with side lengths a and b has perimeter 2(a + b) and area ab.
Use length units for its boundary and square units for its area.
Exercises with solutions
The perimeter is the length of the boundary: U = 2 · (a + b). The area is the size of the surface itself: A = a · b. Because the two are easily confused, the unit helps: the perimeter has cm or m, the area always cm² or m².
Exercise 1
A rectangle is 7 cm long and 4 cm wide. Calculate the perimeter.
Show solution and working
22 cm
U = 2 · (7 cm + 4 cm) = 2 · 11 cm = 22 cm.
Exercise 2
A rectangle is 7 cm long and 4 cm wide. Calculate the area.
Show solution and working
28 cm²
A = 7 cm · 4 cm = 28 cm².
Exercise 3
A square has side length 5 cm. Calculate perimeter and area.
Show solution and working
U = 20 cm, A = 25 cm²
In a square all sides are equal: U = 4 · 5 cm = 20 cm and A = 5 cm · 5 cm = 25 cm².
Exercise 4
A rectangle has perimeter 30 cm and length 9 cm. How wide is it?
Show solution and working
6 cm
Half the perimeter is 30 cm ÷ 2 = 15 cm. Subtract the length: 15 cm − 9 cm = 6 cm.
Common mistake
Swapping perimeter and area. Picture the perimeter as a fence around the surface and the area as the lawn inside. The unit also tells you which one is wanted.
Maths by grade
Keep learning with MatheJump
Create a free account and explore math practice. Choose from the available exercises to suit your learning needs.