16. A pump can fill that tank in 4 hrs because of a leak in the tank it took 5(1/2) hours to fill the tank.If the tank is full how much time will the leak take to empty it?

A. 13 hrs B. 12 hrs 50 mins C. 14 hrs 40 mins D. 14 hrs

Answer Answer: Option C Explanation: Time taken by leak to empty the tank = 1/4-1/(11/2) = 1/4-2/11
11-8/44 = 3/44
44/3 = 14(2/3) = 14 hrs 40 mins

17. Two pipes A & B can fill a tank in 20 minutes.If both pipes are opened simultaneously after how much time should B be closed so that the tank is full in 18 minutes?

A. 10 mins B. 9 mins C. 8 mins D. None of these

Answer Answer: Option D Explanation: A fill the tank in1 minute = (20*20=40) = 2 units
B fill the tank in 1 minute = (40*1=40) = 1 unit
For 18 minutes (A) = 18 *2 = 36 units
Remaining = 40-36 = 4 units
Time for B be closed so that the tank is full in 18 minutes = 4/1 = 4 minutes

19. A tap can fill a tank in 6 hrs. After half the tank is filled 3 more similar taps are opened. What is the total time taken to fill the tank completely?

A. 3 hrs B. 3 hrs 30 mins C. 3 hrs 45 min D. 4 hrs

Answer Answer: Option C Explanation: Time taken to fill the half time = 6/2 = 3hrs (1/2 part is filled)
Remaining time = 1/2
Time taken to fill the remaining part =( 1/(4*1/6))*(1/2) = (3*1)/(2*2)=3/4 hrs = 45 mins
Total time 3 hrs + 45 mins =3hrs 45 minutes

20. Two pipes can fill a tank in 6 hrs and 8 hrs while a 3'rd pipe empties the full tank in 12 hrs.If all 3 pipes are operator simultaneously in how much time will the tank be filled ?

A. 4 hrs B. 4 hrs 28 mins C. 5 hrs D. 5 hrs 35 mins

Answer Answer: Option B Explanation: 1/6+1/8-1/12 = (4+3-2) / 24 = 5/24
Time taken to fill the tank = 24/5
therefore total time taken is 4 hrs and 28 minutes