Two pipes P and Q can fill a cistern in 12 min. and 15 min. respectively but a third pipe ‘R’ can empty the full tank in 6 min.  P and Q are kept open for 5 min. in the beginning and then ‘R’ is also opened.  In what time is the cistern emptied ?

Related Mcqs:

1. 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

2. 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

3. 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

4. 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

5. wo pipes X and Y fill a tank in 15 hrs. and 20 hrs. respectively, while a third pipe ‘Z’ can empty the full tank in 25 hrs.  All the three pipes are opened in the beginning.  After 10 hrs. Z is closed.  In how much time, will the tank be full ?

   A. 12 hrs
   B. 14 hrs
   C. 16 hrs
   D. 18 hrs

6. Two pipes A and B can fill a tank in 15 min and 20 min respectively. Both the pipes are opened together but after 4 min, pipe A is turned off. What is the total time required to fill the tank?

   A. 10 min 20 sec
   B. 11 min 45 sec
   C. 12 min 30 sec
   D. 14 min 40 sec

7. A tank is filled by three pipes with uniform flow. The first two pipes operating simultaneously fill the tank in the same during which the tank is filled by the third pipe alone. The second pipe fills the tank 5 hours faster than the first pipe and 4 hours slower than the third pipe. The time required by the first pipe is?

   A. 6 hrs
   B. 10 hrs
   C. 15 hrs
   D. 30 hrs

8. Two pipes can fill a tank in 18 minutes and 15 minutes. An outlet pipe can empty the tank in 45 minutes. If all the pipes are opened when the tank is empty, then how many minutes will it take to fill the tank?

   A. 12
   B. 13
   C. 11
   D. 10

9. 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

10. Three pipes A, B and C can fill a tank from empty to full in 30 minutes, 20 minutes and 10 minutes respectively. When the tank is empty, all the three pipes are opened. A, B and C discharge chemical solutions P, Q and R respectively. What is the proportion of solution R in the liquid in the tank after 3 minutes?

    A. 5/11
    B. 6/11
    C. 7/11
    D. 8/11