Pipe A can fill a tank in 5 hours, pipe B in 5 hours and pipe C in 10 hours. If all the pipes are open, in how many hours will the tank be filled?	Options
A) 5  B) 4  C) 3  D) 1  E) 2
Part filled by A + B + C in 1 hour = 1/5 + 1/5+ 1/10= 1/2   All the three pipes together will fill the tank in 2 hours.   Answer: 2
<result>E</result>
Pipe A can fill a tank in 5 hours, pipe B in 5 hours and pipe C in 10 hours. If all the pipes are open, in how many hours will the tank be filled?