The area of the cloud (circle) is
Substitute R(t) into the formula to get
Differentiate A(t) with respect to t, then substitute t=4 into your equation for to get your answer in square metres per hour.
A circular cloud of poison gas from a factory explosion is expanding so that t hours after the explosion the radius of the cloud is meters. How fast is the area of the cloud increasing 4 hours after the explosion?
________________________square meters per hour
I've tried about 11 different answers and none of them have worked out, help?