Mark the correct alternative in the following:

A cone whose height is always equal to its diameter is increasing in volume at the rate of 40 cm3/sec. At what rate is the radius increasing when its circular base area is 1 m2?


The volume of a cone, with height h and radius r, is defined by

- (1)


Given that h=2r, we get - (1)


and πr2=1m2=10000cm2, we have to find out


Differentiating (1) with respect to t, we get



Substituting the values, we get



1