dealing with volume in a spherical balloon

[kggirl]

A spherical balloon is being inflated. The volume = 4/3pi r^3 When r = 10.0 cm, the radius is increasing at the rate of dr/dt = 1.00cm/s. How fast is the volumeincreasing at that time? (What is the dV/dt?)

 

[wgunther]

V=4/3pi r³

You have to differentiate in respect to time (t)

dV/dt=4pi r² dr/dt

You know dr/dt. and you know r for that time