Question

Find the rate of change of the area of a circle per second with respect to
its radius r when r = 5 cm.

Answer 1

@ParthKohli

Answer 2

Differentiate \(\pi r^2\) with respect to \(r\).

Answer 3

When you find \(f'(r)\), find \(f'(5)\)

Answer 4

Thanks

Answer 5

The answer turns out to be the circumference.

Answer 6

Actually shouldn't it be like this,
$$A=\pi r^2$$
Since rate of change is associated with 'time'
differentiation with respect to 't'- time,
$$\frac{dA}{dt}=\pi\frac{dr^2}{dt}=2\pi r\frac{dr}{dt}$$
rate of change in radius should be given