Pipes A and B can fill a tank in 3 and 6 hours respectively. Pipe C can empty it in 12 hours. If all the three pipes are opened together, then the tank will be filled in? Choose the correct choice from the following answers
A) 3 9/97 hrs  B) 3 9/77 hrs  C) 3 9/17 hrs  D) 3 9/27 hrs  E) 2 2/5 hrs
Net part filled in 1 hour = 1/3 + 1/6 - 1/12   = 5/12   The tank will be full in 12/5 hrs, i.e., 2 2/5 hrs.   Answer:2 2/5 hrs
<result>E</result>
Pipes A and B can fill a tank in 3 and 6 hours respectively. Pipe C can empty it in 12 hours. If all the three pipes are opened together, then the tank will be filled in?