**(1)** A pipe can fill a tank in 4 hours, and a leak at the bottom can empty it in 8 hours. If both are opened simultaneously when the tank is empty, in how much time will the tank be filled?

- (a) 7 hours
- (b) 8 hours
- (c) 12 hours
- (d) 6 hours

**(2)** Two pipes A and B can fill a cistern in 20 minutes and 30 minutes respectively. They are opened one after another with an interval of 5 minutes. How long will it take to fill the cistern?

- (a) 23 minutes
- (b) 25 minutes
- (c) 27 minutes
- (d) 28 minutes

**(3)** Pipe A can fill a tank three times as fast as Pipe B. If together they can fill the tank in 36 minutes, how long will Pipe B alone take to fill the tank?

- (a) 144 minutes
- (b) 108 minutes
- (c) 96 minutes
- (d) 72 minutes

**(4)** Pipe X can fill a tank in 6 hours, while Pipe Y can fill the same tank in 8 hours. If both pipes are opened simultaneously when the tank is empty, how long will it take to fill the tank?

- (a) 3 hours
- (b) 3.43 hours
- (c) 4 hours
- (d) 4.5 hours

**(5)** Pipe A can fill a cistern in 10 hours, and Pipe B can empty the same cistern in 20 hours. If both pipes are opened simultaneously when the cistern is empty, how long will it take to fill the cistern completely?

- (a) 15 hours
- (b) 10 hours
- (c) 30 hours
- (d) 40 hours