Page 103 - Maths Skill - 6

Perimeter and Area 101

Let’s Attempt

Example 1: Find the perimeter of each of the following figures:

(i) (ii) (iii) (iv)

Solution: To find the perimeter of each of the above figures, we add the measure of all the sides (clockwise
or anticlockwise as per convenience):
(i) Perimeter = (2 + 5 + 7 + 9) cm = 23 cm
(ii) Perimeter = (15 + 25 + 20 + 20) cm = 80 cm

(iii) Perimeter = (12 + 12 + 12 + 12) cm = 48 cm
(iv) Perimeter = (7 + 7 + 7 + 7 + 7 + 7) cm = 42 cm

Example 2: The lid of a rectangular box of sides 40 cm by 20 cm is sealed all round with a tape. What is the
length of the tape required?
Solution: Length of the lid = 40 cm
Breadth of the lid = 20 cm
Length of the tape required = Perimeter of the lid

= 2 (Length + Breadth)
= 2 (40 + 20) cm = 2 × 60 cm = 120 cm

Example 3: A rectangular piece of land measures 0.5 km by 0.2 km. Each side is to be fenced with 2 rows of
wires. What is the length of the wire needed?
Solution: Length of the piece of land = 0.5 km
Breadth of the piece of land = 0.2 km
Perimeter of the piece of land = 2 (Length + Breadth)

= 2 (0.5 + 0.2) km = 1.4 km
Since each side is to be fenced twice, therefore the length of the wire needed
= 2 × 1.4 km = 2.8 km

Example 4: Find the perimeter of each of the following shapes:
(i) A scalene triangle of sides 6 cm, 7 cm and 8 cm
(ii) An equilateral triangle of side 8 cm
(iii) An isosceles triangle with equal sides 7 cm each and third side 4 cm

Solution: (i) Perimeter of a scalene triangle = Sum of measures of its sides
= 6 cm + 7 cm + 8 cm = 21 cm

(ii) Perimeter of an equilateral triangle = 3 × Side = 3 × 8 cm = 24 cm
(iii) Perimeter of an isosceles triangle = Sum of measures of its sides
= 7 cm + 7 cm + 4 cm = 18 cm