(6) Pipe P can fill a tank in 5 hours, and Pipe Q can fill the same tank in 7 hours. Pipe R can empty the tank in 10 hours. If all three pipes are opened simultaneously when the tank is empty, how long will it take to fill the tank?
- (a) 4 hours
- (b) 5 hours
- (c) 14 hours
- (d) 20 hours
(7) Pipe A can fill a tank in 12 hours, and Pipe B can fill the same tank in 16 hours. Pipe C can empty the tank in 8 hours. If all three pipes are opened simultaneously when the tank is empty, how long will it take to fill the tank?
- (a) 4 hours
- (b) 6 hours
- (c) 8 hours
- (d) 10 hours
(8) Pipe A can fill a tank in 15 hours, and Pipe B can fill the same tank in 20 hours. Pipe C can empty the tank in 30 hours. If all three pipes are opened simultaneously when the tank is empty, how long will it take to fill the tank?
- (a) 10 hours
- (b) 24 hours
- (c) 30 hours
- (d) 40 hours
(9) Pipe X can fill a tank in 3 hours, and Pipe Y can empty the same tank in 5 hours. If both pipes are opened simultaneously when the tank is empty, how long will it take to fill the tank?
- (a) 2 hours
- (b) 3 hours
- (c) 4 hours
- (d) 6 hours
(10) Pipe A can fill a cistern in 12 hours, and Pipe B can empty the same cistern in 18 hours. If both pipes are opened simultaneously when the cistern is empty, how long will it take to empty the cistern completely?
- (a) 6 hours
- (b) 9 hours
- (c) 36 hours
- (d) 24 hours
