Exercise 16.4
Find the circumference of the circles whose radii are given belov
) 12 m
(b) 19.7 cm
(c) 22.5 m
(d) 46.6 cm
Answers
From the properties of circles : -
- Circumference of circle = 2πr, where r represents the radius of circle and numeric value of π is 22 / 7 or 3.14.
a ) : 12 m
= > Circumference of circle with radius of 12 m = 2 x π x 12 m
= > 2 x 12 x 22 / 7 m or π x 12 m
= > 24 x 22 / 7 m or 24π m
= > 75.43 m or 24π m
Hence the required circumference is 24π m.
b ) : 19.7 cm
= > Circumference of circle with radius of 19.7 cm = 2 x π x 19.7 cm
= > 2 x 19.7 x 22 / 7 cm or π x 2 x 19.7 cm
= > 39.4 x 22 / 7 cm or 39.4 π cm
= > 123.81 cm or 39.4π cm
Hence the required circumference is 39.4 cm.
c ) : 22.5 m
= > Circumference of circle with radius of 22.5 m = 2 x π x 22.5 m
= > 2 x 22.5 x 22 / 7 m or π x 2 x 22.5 m
= > 45 x 22 / 7 m or 45π m
= > 141.41 m or 45π m
Hence the required circumference is 45π m.
d ) : 46.6 cm
= > Circumference of circle with radius of 46.6 cm = 2 x π x 46.6 cm
= > 2 x 44.6 x 22 / 7 cm or π x 2 x 44.6 cm
= > 89.2 x 22 / 7 cm or 89.2π cm
= > 280.33 m or 89.2π m
Hence the required circumference is 89.2 π cm.