If the circumference of a circle of radius 'r' and the perimeter of a square of side 'a' are equal , then the ratio of area of the circle to that of the square is :
(A) 4:pie

(B) pie:4

(C) pie²:16

(D) pie²:4

Radius of the circle = r

Circumference of the circle = 2πr

Side of the square = a

Perimeter of the square = 4a.

Given, Circumference of the circle = Perimeter of square

∴ 2πr = 4a

Thus, the ratio of area of the circle to that of the square is 4 : π.