List of top Quantitative Aptitude Questions on Pipes & Cisterns asked in CAT

Pipes A and C are fill pipes while Pipe B is a drain pipe of a tank. Pipe B empties the full tank in one hour less than the time taken by Pipe A to fill the empty tank. When pipes A, B and C are turned on together, the empty tank is filled in two hours. If pipes B and C are turned on together when the tank is empty and Pipe B is turned off after one hour, then Pipe C takes another one hour and 15 minutes to fill the remaining tank. If Pipe A can fill the empty tank in less than five hours, then the time taken, in minutes, by Pipe C to fill the empty tank is

A pipe can fill a tank in 6 hours, and another pipe can empty it in 8 hours. If both pipes are opened together, how long will it take to fill the tank?

A chemical plant has four tanks (A, B, C, D), each containing $1000$ litres. Chemical is pumped between tanks at the given rates:
A → B: 20 L/min,
C → A: 90 L/min,
A → D: 10 L/min,
C → D: 50 L/min,
B → C: 100 L/min,
D → B: 110 L/min.
Which tank empties first and how long does it take (minutes) after pumping starts?