Related Rates Calculus question - A helium balloon

Question

Helium is pumped into a spherical balloon at a rate of 5 cubic feet per second. How fast is the radius increasing after 2 minutes?Note: The volume of a sphere is given by  V = (4/3)pi*r^3

Answer 1

V = t dV/dt

After 2 minutes

V= 120(5) = 600 ft³

V = (4/3)πr³ --> r = ((3/(4π))V)^1/3 =(1800/(4π))^1/3 ≈ 5.23 ft

dV/dt = 4πr² dr/dt

dr/dt = (dV/dt)/(4πr²) = 5/((4π)5.23²) ≈ 0.0145 ft/min