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example 1. What is the perimeter of these shapes?

a. b. c.

Solution. a. b. c.

The perimeter of a polygon is the sum of the lengths of the line segments that enclose
the figure.

i.e., Perimeter of a polygon = Sum of the lengths of its sides
example 2. Find the perimeter of the following shapes. Which shape has the greater

perimeter?

Solution. Perimeter of shape P = Sum of the sides

= 5 m + 8 m + 10 m + 16 m = 39 m
Perimeter of shape Q = Sum of the sides
= 8 m + 3 m + 5 m + 10 m + 5 m + 2 m + 8 m + 15 m = 56 m
Thus, shape Q has the greater perimeter.

example 3. The perimeter of a triangle is 26 cm. If the lengths of two sides of the
triangle are 8 cm and 12 cm respectively, find the length of its third side.

Solution. Let PQR be a triangle such that PQ = 8 cm and QR = 12 cm
The perimeter of triangle PQR = PQ + QR + PR
Perimeter = 26 cm P
Sum of two given sides = 8 cm + 12 cm = 20 cm 8 cm ?

Length of the third side = Perimeter – Sum of two sides
= 26 cm – 20 cm = 6 cm Q 12 cm R

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Perimeter and Area