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,

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

.

∴When r = 6 cm,

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

The correct answer is B.