Page 191 - Touchpad Mathematics_Ver1.0_C5

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example 1. Find the perimeter of the following shapes:

a. b. c.
1 unit 1 unit 3 1 unit 3
3
1 1 1
2 1 1
2 4 2 2 4 4

2 1 1 1 1 1
3 3 3

Solution. a. Perimeter = Sum of the lengths of the outer boundary
= (2 + 1 + 3 + 4 + 3 + 1 + 2 + 2) units = 18 units

b. Perimeter = (2 + 1 + 1 + 3 + 1 + 1 + 2 + 1 + 1 + 3 + 1 + 1) units = 18 units
c. Perimeter = (4 + 3 + 4 + 3) units = 14 units

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.

A triangle, rectangle and square are also rectilinear figures. Let us learn how we
can find the perimeter of these figures.

Perimeter of a rectangle

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
[Since AB = CD and AD = BC]

= 2(AB + BC)

= 2(Length + Breadth)
Hence, Perimeter of a rectangle = 2(Length + Breadth).

189
Perimeter and Area