A spherical party balloon is being inflated with helium pumped in at a rate of 12 cubic feet per minute. How fast is the radius growing at the instant when the radius has reached 1 ft?

Answer 1

V = 4/3*PI*r^3

dV/dt = 12 = 4*PI*r^2*dr/dt = 4*PI*1^2*dr/dt

Solve for dr/dt, the rate at which the radius is growing