Pipes A and B can fill a tank in 16 hours and 24 hours, respectively, whereas pipe C can empty the full together, but pipe A nk in 40 hours. All three pipes are opened together, but pipe A is closed after 10 hours, After how many hours will the remaining part of the tank be filled?
Show answer & explanation
Correct answer: B
Explanation
The correct answer is option 2 i.e. 12
Pipe A can fill in 16 hours.
Pipe B can fill in 24 hours.
Pipe C can empty in 40 hours.
If a pipe can fill or empty in A hours, then it can fill or empty 1/A part in 1 hour.
Pipe A can fill 1/16 in 1 hour.
Pipe B can fill 1/24 in 1 hour.
Pipe C can empty 1/40 in 1 hour.
Together they can fill (1/16 + 1/24 - 1/40) = 19/240 part in 1 hour
Together they can fill 190/240 = 19/24 parts in 10 hours
Remaining tank = 1 - 19/24 = 5/24
B and C can fill (1/24 - 1/40) = 1/60 in 1 hour.
B and C can fill a tank in 60 hours
B and C can fill the 5/24 of the remaining tank = 60 × 5/24 = 25/2 = 12.5 hours
The remaining tank will be filled in 12 1/2 hours.