Question

find the circumference of circle whose area is 4 times the other of a circle with diameter 21 CM

Answer 1

Radius of the circle = 21/2

Area of given circle = π r^2 = 346.185

Area of the first circle = 4 × Area of second

= 1384.74

πR^2 = 1384.74

R^2 = 440.60

R = 21 ( Approx)

Circumference = 2πr = 2 ×3.14×21

= 131.88 Ans

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