Pipe A can fill a tank in 6 hours, pipe B in 12 hours and pipe C in 36 hours. If all the pipes are open,in how many hours will the tank be filled ?	Pick one.
A) 3.2	B) 3	C) 3.3	D) 3.5	E) 3.6
1/6+1/12+1/36=10/36=1/3.6. so 3.6 hrs   ANSW3.6R:3.6
<result>E</result>
Pipe A can fill a tank in 6 hours, pipe B in 12 hours and pipe C in 36 hours. If all the pipes are open,in how many hours will the tank be filled ?