Question

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
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Answer 1

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.$\:$