Page 152 - Math Skill - 4

150 Maths

Let’s Attempt

Example 1: In a triangle PQR, PQ = 3 cm, QR = 4 cm and RP = 5 cm. Find its perimeter.
Solution: Perimeter of ∆PQR = Sum of all sides P
= PQ + QR + RP

= 3 cm + 4 cm + 5 cm 3 cm 5 cm
= 12 cm

Hence, the perimeter of ∆PQR is 12 cm. Q 4 cm R
Example 2: Find the perimeter of a quadrilateral ABCD with AB = 2 cm, BC = 5 cm, CD = 3 cm
and DA = 4 cm.

Solution: Perimeter of quadrilateral ABCD = sum of all sides

4 cm D = AB + BC + CD + DA

A = 2 cm + 5 cm + 3 cm + 4 cm
2 cm 3 cm
= 14 cm
B C
5 cm
Hence, perimeter of quadrilateral is 14 cm.

Example 3: Find the perimeter of the following figures.
Solution: (a) 2 cm (b) 3 cm

3 cm 1 cm
3 cm
5 cm

4 cm 1 cm
4 cm 3 cm

Solution: (a) Perimeter = 2 cm + 3 cm + 4 cm + 4 cm + 3 cm = 16 cm
(b) Perimeter = 5 cm + 3 cm + 1 cm + 1 cm + 3 cm = 13 cm

Perimeter of a Rectangle

A rectangle has its opposite sides equal.
Let us take a rectangle ABCD and find its perimeter. A Length B
Perimeter of a rectangle ABCD

= AB + BC + CD + DA Breadth Breadth
= AB + BC + AB + BC C
[AB = CD and BC = DA] D Length

= 2 AB + 2 BC = 2 (AB + BC)
Hence, Perimeter of a rectangle = 2 × (length + breadth)