Pipe A can fill a tank in 3 hours, pipe B in 4 hours, and pipe C in 6 hours. If all the pipes are open, in how many hours will the tank be filled?  Choose one.
A) 1  B) 1.3  C) 1.6  D) 1.9  E) 2.2
The part filled by A + B + C in 1 hour is 1/3 + 1/4 + 1/6 = 3/4   All the three pipes together will fill the tank in about 1.3 hours.   The answer is 1.3.
<result>B</result>
Pipe A can fill a tank in 3 hours, pipe B in 4 hours, and pipe C in 6 hours. If all the pipes are open, in how many hours will the tank be filled?