Browse Questions

# The rate of change of area $A$ of circle of a radius $r$ is

$\begin{array}{1 1}(1)2\pi r&(2)2\pi r\frac{dr}{dt}\\(3)\pi r^{2}\frac{dr}{dt}&(4)\pi\frac{dr}{dt}\end{array}$

Can you answer this question?

Let A be the radius of the circle at time 't'
$A= \pi r^2$