The Total solution for NCERT class 6-12
The rate of change of the area of a circlewith respect to its radius r at r = 6 cm is
(A) 10π (B) 12π (C) 8π (D) 11π
The area of a circle (A) withradius (r) is given by,
Therefore, the rate of change of the areawith respect to its radius r is
∴When r = 6 cm,
Hence, the required rate of change of thearea of a circle is 12π cm2/s.
The correct answer is B.