Area and Perimeter Formulas • Topic 1 of 3

Perimeter of Rectangle and Square

Perimeter is the total distance around the outside of a shape — like walking around the boundary of a park.

Rectangle:
Perimeter = 2 x (Length + Width)
P = 2 x (l + w)

Why? A rectangle has 2 equal lengths and 2 equal widths.

Square:
All four sides are equal.
Perimeter = 4 x side (P = 4s)

To find a missing side: rearrange the formula. E.g. if P = 36 and l = 10, then 36 = 2(10+w), so w = 8.

Perimeter FormulasRectangleLength = 8 cmW=5P = 2(8+5) = 26 cmSquare6 cmP = 4 x 6 = 24 cm6 cm
Solved Examples
1
Worked Example
A rectangular garden is 12 m long and 8 m wide. Find its perimeter.
SolutionP = 2 x (l + w) = 2 x (12 + 8) = 2 x 20 = 40 m. Answer: 40 m.
2
Worked Example
A square playground has a side of 25 m. What is its perimeter?
SolutionP = 4 x s = 4 x 25 = 100 m. Answer: 100 m.
3
Worked Example
A rectangle has a perimeter of 36 cm. Its length is 10 cm. Find the width.
SolutionP = 2(l + w). 36 = 2(10 + w). 18 = 10 + w. w = 18 - 10 = 8 cm. Answer: 8 cm.

Key Points

  • Perimeter measures the distance AROUND the boundary of a shape
  • Rectangle: P = 2 x (l + w) because it has 2 lengths and 2 widths
  • Square: P = 4 x s because all four sides are equal
  • To find missing side: rearrange the perimeter formula
Quick Check — 4 MCQs
Tap an option to check your answer0 / 4
Q1.Perimeter is the total length:
Explanation: Around the boundary.
Q2.Perimeter of a rectangle is:
Explanation: $2(l+b)$.
Q3.Perimeter of a square is:
Explanation: $4\times\text{side}$.
Q4.A square of side $5$ has perimeter:
Explanation: $4\times5=20$.
Practice more MCQs → 📝 Assignment · 35 marks