## 9 3 years ago Suppose a forest fire spreads in a circle with radius at rate of 5 per minute. when the radius reaches 200 feet, at what rate is the area of the burning region increasing?

$\frac{dr}{dt}=5$$\frac{dA}{dt}=2 \pi r\frac{dr}{dt}=10 \pi r$For r=200, the rate is 2000pi