Pipe A can fill a tank in 4 hours, pipe B in 8 hours and pipe C in 16 hours. If all the pipes are open, in how many hours will the tank be filled ?  Choose the correct answer:
A) 2.5 hours  B) 2 hours  C) 3.5 hours  D) 2.3 hours  E) None of these
Explanation:   Part filled by A in 1 hour = 1/4   Part filled by B in 1 hour = 1/8   Part filled by C in 1 hour = 1/16   Part filled by (A+B+C) in 1 hour =   1/4+1/8+1/16=7/16   So all pipes will fill the tank in 2.3 hours.   Option 2.3 hours
<result>D</result>
Pipe A can fill a tank in 4 hours, pipe B in 8 hours and pipe C in 16 hours. If all the pipes are open, in how many hours will the tank be filled ?