A cistern can be filled by a tap in 3 hours while it can be emptied by another tap in 6 hours. If both the taps are opened simultaneously, then after how much time will the cistern get filled?  Pick:
A) 5.2 hrs  B) 2.9 hrs  C) 1.9 hrs  D) 6 hrs  E) 5 hrs
Net part filled in 1 hour = (1/3 - 1/6) = 1/6   The cistern will be filled in 6/1 hrs i.e., 6 hrs.   Answer:6 hrs
<result>D</result>
A cistern can be filled by a tap in 3 hours while it can be emptied by another tap in 6 hours. If both the taps are opened simultaneously, then after how much time will the cistern get filled?