Q. If a tank can be filled by a pipe in 20 hours and emptied by another pipe in 30 hours, how long will it take to fill the tank if both pipes are opened together?
A.12 hours
B.15 hours
C.18 hours
D.24 hours
Solution
The net rate is 1/20 - 1/30 = 1/60. Therefore, it will take 60 hours to fill the tank.
Q. If a tank can be filled by a pipe in 20 minutes and emptied by another pipe in 30 minutes, how long will it take to fill the tank if both pipes are opened together?
A.10 minutes
B.15 minutes
C.20 minutes
D.25 minutes
Solution
The net rate is 1/20 - 1/30 = 1/60. Therefore, it will take 60 minutes to fill the tank.
Q. If a tank can be filled by a pipe in 25 minutes and emptied by another pipe in 50 minutes, how long will it take to fill the tank if both pipes are opened together?
A.16.67 minutes
B.20 minutes
C.25 minutes
D.30 minutes
Solution
The net rate is 1/25 - 1/50 = 1/50. Therefore, it will take 50 minutes to fill the tank.
Q. If a tank can be filled by a pipe in 8 hours and emptied by another pipe in 12 hours, how long will it take to fill the tank if both pipes are opened together?
A.4 hours
B.6 hours
C.8 hours
D.10 hours
Solution
The net rate is 1/8 - 1/12 = 1/24. Therefore, it will take 24 hours to fill the tank.
Q. Pipe A can fill a tank in 15 hours, and pipe B can fill the same tank in 20 hours. If both pipes are opened together, how long will it take to fill the tank?
A.6 hours
B.8 hours
C.10 hours
D.12 hours
Solution
The combined rate is 1/15 + 1/20 = 7/60. Therefore, it will take 60/7 hours, approximately 8.57 hours to fill the tank.
Q. Pipe A can fill a tank in 15 hours, while pipe B can fill it in 10 hours. If both pipes are opened together, how long will it take to fill the tank?
A.4 hours
B.5 hours
C.6 hours
D.7 hours
Solution
The combined rate is 1/15 + 1/10 = 1/6. Therefore, it will take 6 hours to fill the tank.
Q. Pipe A can fill a tank in 6 hours, and pipe B can fill the same tank in 9 hours. If both pipes are opened together, how long will it take to fill the tank?
A.2 hours
B.3 hours
C.4 hours
D.5 hours
Solution
The combined rate is 1/6 + 1/9 = 5/18. Therefore, it will take 18/5 = 3.6 hours to fill the tank.
Q. Two pipes can fill a tank in 10 hours and 15 hours respectively. If the first pipe is opened for 5 hours and then the second pipe is opened, how long will it take to fill the tank?
A.3 hours
B.4 hours
C.5 hours
D.6 hours
Solution
The first pipe fills 1/2 of the tank in 5 hours. The remaining half can be filled by both pipes in 2 hours.
