## anonymous 5 years ago A single hailstone falls into a pool at the beginning of a thunderstorm. It makes a circular ripple. The radius increases at 2 cm/s, when the radius is 5cm. What is the rate of change of the area enclosed at this time?

1. anonymous

$\frac{1}{5\pi}\frac{cm}{s}$

2. anonymous

i.e. $A=\pi r^2$ $\frac{dA}{dt}=2\pi r\frac{dr}{dt}$ $\frac{dr}{dt}=\frac{\frac{dA}{dt}}{2\pi (5)}$

3. anonymous

Thank you!!