A. 1 hr
B. 2 hrs
C. 6 hrs
D. 8 hrs
Explanation:
Let the cistern be filled by pipe A alone in x hours.
Then, pipe B will fill it in (x + 6) hours.
1/x + 1/(x + 6) = 1/4
x2 – 2x – 24 = 0
(x – 6)(x + 4) = 0 => x = 6.
Related Mcqs:
- Two pipes A and B can separately fill a cistern in 60 min and 75 min respectively. There is a third pipe in the bottom of the cistern to empty it. If all the three pipes are simultaneously opened, then the cistern is full in 50 min. In how much time, the third pipe alone can empty the cistern?
A. 90 min
B. 100 min
C. 110 min
D. 120 min - Two pipes A and B can separately fill a cistern in 10 and 15 minutes respectively. A person opens both the pipes together when the cistern should have been was full he finds the waste pipe open. He then closes the waste pipe and in another 4 minutes the cistern was full. In what time can the waste pipe empty the cistern when fill?
A. 7 min
B. 8 min
C. 9 min
D. 10 min - Two pipes can separately fill a tank in 20 and 30 hours respectively. Both the pipes are opened to fill the tank but when the tank is full, a leak develops in the tank through which one-third of water supplied by both the pipes goes out. What is the total time taken to fill the tank?
A. 18 hrs
B. 16 hrs
C. 15 hrs
D. 12 hrs - A cistern has three pipes, A, B and C. The pipes A and B can fill it in 4 and 5 hours respectively and C can empty it in 2 hours. If the pipes are opened in order at 1, 2 and 3 A.M. When will the cistern be empty?
A. 3 PM
B. 7 PM
C. 4 PM
D. 5 PM - One top can fill a cistern in 2 hours and another can empty the cistern in 3 hours. How long will they take to fill the cistern if both the taps are opened?
A. 5 Hours
B. 6 Hours
C. 7 Hours
D. 8 Hours - A pipe can fill a cistern in 20 minutes whereas the cistern when fill can be emptied by a leak in 28 minutes. When both pipes are opened, find when the cistern will be full?
A. 60 min
B. 80 min
C. 70 min
D. 48 min - Three pipes A, B and C can fill a tank in 6 hours. After working at it together for 2 hours. C is closed A and B can fill the remaining par in 7 hours. The number of hours taken by C alone to fill the tank is?
A. 10
B. 12
C. 14
D. 16 - A cistern has two taps which fill it in 12 min. and 15 min.respectively There is one outlet pipe in the cistern. When all the taps & pipe are opened, the empty cistern is full in 20 min. How long will the waste pipe (outlet) take to empty the full cistern ?
A. 10 min
B. 20 min
C. 30 min
D. 40 min - A cistern is filled by a tap in 3 1/2 hours. Due to leak in the bottom of the cistern, it takes half an hour longer to fill the cistern. If the cistern is full how long will it take the leak to empty it?
A. 7 hours
B. 8 hours
C. 14 hours
D. 28 hours - If two pipes function together, the cistern will be filled in 6 hrs. One pipe fills the cistern 5 hrs. faster than the other. How many hours it take the second pipe to fill the cistern?
A. 5 hrs
B. 10 hrs
C. 15 hrs
D. 20 hrs
