V = pi R^2 h
dV/dR = pi h (2 R ) = 2 R pi h
so
dV/dt = h * (2 pi R) dR/dt
or in other words h times the circumference * dR /dt (sketch it :)
The volume of a cylinder of height 11 inches and radius r inches is given by the formula V=11πr2 .
Suppose that the radius is expanding at a rate of 0.4 inches per second. How fast is the volume changing when the radius is 2.9 inches? Use at least 5 decimal places in your answer.
answer: ____ cubic inches per second
1 answer