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1. Find the perimeter of the following figures.
( a) (b) 3.6 cm ( c)
20 cm
5 cm 1.7 cm

23 cm 3.6 cm 3.6 cm 4.5 cm

3.6 cm
2. Find the area of the following.

( a) ( b) ( c)

perimeter

The distance around the edges of a closed figure is called its perimeter. We know that
a plane figure bounded by only line segments is called a rectilinear figure. A triangle,
rectangle and square are rectilinear figures. The sum of the lengths of all the sides of a
rectilinear figure is called its perimeter.

Look at some rectilinear figures and their perimeters. Let us learn how we can find the
perimeter of these figures.

perimeter of a rectangle
A D
In the given figure, ABCD is a rectangle in which AB, BC, CD and DA
are its sides. We know that the opposite sides of a rectangle are equal.
Perimeter of rectangle ABCD = AB + BC + CD + DA

= AB + BC + AB + BC B C
(Since AB = CD and AD = BC) = 2(AB + BC)
= 2(Length + Breadth)

Perimeter of a rectangle = 2(Length + Breadth)

Example 1: Find the perimeter of a rectangle whose length is 12 cm and breadth is 7 cm.
Solution: Length of the rectangle = 12 cm and breadth of the rectangle = 7 cm

Perimeter of the rectangle = 2 (Length + Breadth) 12 cm
= 2(12 + 7) cm
7 cm
= 2 × 19 cm = 38 cm
Hence, the perimeter of the rectangle is 38 cm.

Teacher’s Explain to students that they can also use the short form for any formula. For example, the perimeter of a
Tip rectangle can also be written as P = 2(l + b), where P stands for perimeter, l for length and b for breadth.

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