Q. 344.5( 4 Votes )

The circumference of a circle whose area is 81πr2, is
A. 9πr

B. 18πr

C. 3πr

D. 81πr

Answer :

Let the radius of the circle be R


Area of circle = πR2


81 πr2 = πR2


R = r


R = 9r


Circumference = 2 πr


2πR


2 π(9r)


18 πr

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