Question : Pipes A and B can fill a tank in 16 hours and 24 hours, respectively, whereas pipe C can empty the full tank in 40 hours. All three pipes are opened together, but pipe C is closed after 10 hours. After how many hours will the remaining part of the tank be filled?
Option 1:
Option 2:
Option 3:
Option 4:
Correct Answer:
Solution :
Total Work = Least Common Multiple (LCM) of 16, 24, and 40 = 240
Let the total capacity of the tank be 240 units
Efficiency of A =
= 15 units
Efficiency of B =
= 10 units
Efficiency of C =
= - 6 units (Since C is emptying the pipe)
When all three pipes were opened together for 10 hours,
Work done = (15 + 10 – 6) × 10 = 190 units
Remaining work = 240 units – 190 units = 50 units
Now, Pipe C is closed and the remaining tank will be filled by A and B in =
=
= 2 hours
Hence, the correct answer is