Question

The rate of change of the area of a circle with respect to its radius r at r = 6 cm is

(A) 10π   (B) 12π   (C) 8π    (D) 11π

Answer 1

The area of a circle (A) with radius (r) is given by,

A=πr²

Therefore, the rate of change of the area with respect to its radius r is

Hence, the required rate of change of the area of a circle is 12π cm²/s.
The correct answer is B.