Pipe A can fill a tank in 5 hours, pipe B in 10 hours and pipe C in 30 hours. If all the pipes are open, in how many hours will the tank be filled?
Answers:
A) 2
B) 3
C) 3.5
D) 4
E) 4.5
Part filled by A + B + C in 1 hour = 1/5 + 1/10 + 1/30 = 1/3   All the three pipes together will fill the tank in 3 hours.   ANSWER 3
<result>B</result>
Pipe A can fill a tank in 5 hours, pipe B in 10 hours and pipe C in 30 hours. If all the pipes are open, in how many hours will the tank be filled?