A cistern is filled by pipe A in 10 hours and the full cistern can be leaked out by an exhaust pipe B in 12 hours. If both the pipes are opened, in what time the cistern is full?
Pick one:
A) 50hrs  B) 60hrs  C) 70hrs  D) 80hrs  E) 90hrs
time taken to full the cistern=(1/10-1/12)hrs   =1/60   =60hrs   ANSWER:60hrs
<result>B</result>
A cistern is filled by pipe A in 10 hours and the full cistern can be leaked out by an exhaust pipe B in 12 hours. If both the pipes are opened, in what time the cistern is full?