01-02 Water flowing into cylindrical tank

Problem 01
Water is flowing into a vertical cylindrical tank at the rate of 24 ft³/min. If the radius of the tank is 4 ft, how fast is the surface rising?
 

Solution 01

Problem 02
Water flows into a vertical cylindrical tank at 12 ft³/min, the surface rises 6 in/min. Find the radius of the tank.
 

Solution 02