Page 148 - ICSE Math 5

Perimeter of rectangle PQRS = PQ + QR + RS + SP
= length + breadth + length + breadth

= (2 × length) + (2 × breadth)
= 2 × (length + breadth)

Perimeter of a rectangle = 2 × (length + breadth)

= 2 × (l + b)

Example 2: Find the perimeter of a rectangle whose length is 12 cm and breadth is 7 cm.

Solution: Length (l) = 12 cm and Breadth (b) = 7 cm.
12 cm
 Perimeter of the rectangle = 2 × (l + b)

= 2 × (12 cm + 7 cm)
7 cm 7 cm
= 2 × 19 cm = 38 cm

So, the perimeter of the given rectangle is 38 cm. 12 cm
Example 3: If the length of a rectangular swimming pool is twice its breadth and its breadth is
12 m, find the perimeter of the swimming pool.

Solution: Breadth of the swimming pool (b) = 12 m A l = 2 × 12 m B
Length of the swimming pool (l) = 2 × breadth
b = 12 m
= 2 × 12 m = 24 m
 Perimeter of the swimming pool = 2 × (l + b) D C

= 2 × (24 m + 12 m)
= 2 × 36 m = 72 m

So, the perimeter of the swimming pool is 72 m.

Perimeter of a Square
Side
A square is a simple closed figure whose all 4 sides are of equal D E
lengths.

In the square DEFG given alongside, sides DE, EF, FG and GD are equal.
Side Side
Perimeter of square DEFG = DE + EF + FG + GD
= Side + Side + Side + Side
G F
= 4 × Side Side

Perimeter of a square = 4 × Side

We can also find the length of one side of a square if we know the perimeter of that particular
square using the formula mentioned below.

Perimeter
Side of a square =
4

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