Page 144 - Maths Class 06

Unit of Perimeter
The perimeter of any closed figure is measured in mm, cm, m or km.
1
1 m = 100 cm or 1 cm = m; 1 cm = 10 mm
100
1
2
or 1 mm = cm; 1 km = 1000 m, 1 hectare = 10000 m .
10

NOTE

The opposite sides of a rectangle are equal.
To find the perimeter of a figure, we need to find the length of the boundary.

For examples,

Look at the figures given below. Let us find the perimeter of these figures:
P 2 cm Q N 5 cm M
A 8 cm B 4 cm 9 cm 9 cm

5 cm 6 cm 7 cm R 5 cm S O L

3 cm 3 cm
D 10 cm C U 8 cm T K
(i) (ii) (iii)

1. Perimeter of the Fig. (i) = AB + BC + CD + DA

= 8 cm + 6 cm + 10 cm + 5 cm
= 29 cm
2. Perimeter of the Fig. (ii) = PQ + QR + RS + ST + TU + UP

= 2 cm + 4 cm + 5 cm + 3 cm + 8 cm + 7 cm
= 29 cm

3. Perimeter of the Fig. (iii) = KL + LM + MN + NO OK
+
= 3 cm + 9 cm + 5 cm + 9 cm + 3 cm
= 29 cm

Perimeter of a Rectangle
What do we know about the sides of the rectangle? We know that the opposite
D C
sides are equal.
Since ABand CD are the lengths and BCand DA are the breadths, we can say b
that:
Perimeter of rectangle = length + breadth + length + breadth A l B

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

Perimeter of rectangle = 2 × (l + ) b where, length = l, breadth = b
Mathematics-6 144