Page 338 - Math Smart - 7

15.2.1 Perimeter

You have learnt that a rectangle has two pairs of equal sides and that a square
has four equal sides. The longer side of a rectangle is called its length and the
shorter side is called its width (or breath). The side of a square Is called its length.

5 cm

2 cm 3 cm

Length of the rectangle = 5 cm
Width of the rectangle = 2 cm
Length of the square = 3 cm
The perimeter of a figure is the total length around the edges of the figure.

Find the perimeters of the rectangle and the square.

8 cm b)

5 cm
6 cm

Solution
a) Perimeter of the rectangle = 8 + 8 + 5 + 5
= 2 X (8 + 5) Perimeter = 2 x (Length + Breadth)
= 2 X 13
= 26 cm
b) Perimeter of the square = 6 + 6 + 6 + 6

= 4x6 Perimeter = Length x 4
= 24 cm

Perimeter of a rectangle
= length + breadth + length + breadth

b
The perimeter is the sum = I + b + I +
of the lengths. = (l + b) + {I+ b)
= 2 X (/ +h)
We use units such as mm, length (/)
cm or m, instead of mm^ = 2{l + b)
cm^ and m^.

breadth (b)

Measuring Time, Area, Perimeter and Volume