Pipe A can fill a tank in 8 hours, pipe B in 4 hours and pipe C in 24 hours. If all the pipes are open, in how many hours will the tank be filled?	Choose the correct choice.
A) 1.9 hour B) 2.1 hour C) 4.7 hour D) 2.4 hour E) 3.2 hour
Part filled by pipe A in 1 hour =1/8   Part filled by pipe B in 1 hour =1/4   Part filled by pipe C in 1 hour =1/24   Part filled by pipes A,B,C together in 1 hour=1/8+1/4+1/24=10/24   i.e, pipes A,B,C together can fill the tank in = 24/10= 
<gadget id="calculator">24/10</gadget>
<output>12/5 = around 2.4</output>
2.4 hour.   ANSWER:2.4 hour
<result>D</result>
Pipe A can fill a tank in 8 hours, pipe B in 4 hours and pipe C in 24 hours. If all the pipes are open, in how many hours will the tank be filled?