Question

What is the rate of change of the area of a circle with respect to its radius when, r = 3 cm

Options

• `r`

• `pir`

• `2 pir`

• Zero

Answer 1

`2 pir`

Explanation:

Let 'A' be the area of the circle of radius 'r', then

= `pir^2` and `(dA)/(dr) = 2pir`