Pipe A can fill a tank in 3 hours, pipe B in 4 hours, and pipe C in 12 hours. If all the pipes are open, in how many hours will the tank be filled?	Choose the correct choice from the following choices
A) 1.1  B) 1.3  C) 1.5  D) 1.7  E) 1.9
The part filled by A + B + C in 1 hour is 1/3 + 1/4 + 1/12 = 2/3   All the three pipes together will fill the tank in 1.5 hours.   The answer is 1.5.
<result>C</result>
Pipe A can fill a tank in 3 hours, pipe B in 4 hours, and pipe C in 12 hours. If all the pipes are open, in how many hours will the tank be filled?