Mark the correct alternative in the following:

The radius of a sphere is changing at the rate of 0.1 cm/sec. The rate of change of its surface area when the radius is 200 cm is


The surface area of a sphere, of radius r, is defined by

A(r)=4πr2 – (1)


Given that and r=200cm, we have to calculate


Differentiating (1) with respect to t, we get



Substituting values, we get


1