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 ? Choose the correct choice from the following answers
A) 2 B) 2.5 C) 3 D) 3.5 E) None
Solution   part filled by (A+B+C) in 1 hour	= (1/5 + 1/6 + 1/30)   ‹=› 1/3.   All the three pipes together will fill the tank in 3 hours.   Answer 3
<result>C</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 ?