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 answer:  A) 3.4 hr  B) 2.4 hr  C) 2 hr  D) 2.8 hr  E) 3 hr
Part filled by pipe A in 1 hour = 1/8   Part filled by pipe 2.4 hr in 1 hour = 1/4   Part filled by pipe C in 1 hour = 1/24   Part filled by pipe A, pipe 2.4 hr and pipe C in 1 hour = (1/8)+(1/4)+(1/24)=1024   i.e, pipe A, pipe 2.4 hr and pipe 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 is 2.4 hr
<result>B</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?