Pipe A can fill a tank in 10 hours. Pipe B can fill the same tank in 12 hours. Pipe C can empty the full tank in 16 hours. All the pipes are opened at 8 : 00 A.M. and Pipe A and B are closed at 10 : 00 A.M. After how much time from starting will the tank be empty?

5 hours 52 minutes

A+ = 10 hrs, B+ = 12 hrs, C- = 16 hrs,

⇒ A + B + C opened for 2 hrs and the A + B were closed = (24 + 20 - 15) x 2 = 29 x 2 = 58 units,

⇒ Time required by C to completely empty the tank = \(\frac{58}{15}\) = \( {3 }_{15 }^{13 } \) hrs.

⇒Total time since the start to empty the tank = 2 + \( {3 }_{15 }^{13 } \) = \( {5}_{15 }^{13 } \) x 60 = 5 hours 54 minutes.