Pipe A can fill a tank in 6 hours, pipe B in 8 hours, and pipe C in 24 hours. If all the pipes are open, in how many hours will the tank be filled? Pick one:
A) 2
B) 2.5
C) 3
D) 3.5
E) 4
The part filled by A + B + C in 1 hour is 1/6 + 1/8 + 1/24 = 1/3   All the three pipes together will fill the tank in 3 hours.   The answer is 3.
<result>C</result>
Pipe A can fill a tank in 6 hours, pipe B in 8 hours, and pipe C in 24 hours. If all the pipes are open, in how many hours will the tank be filled?