Pumping alone at their respective constant rates, one inlet pipe fills an empty tank to 1/2 of capacity in 9 hours and a second inlet pipe fills the same empty tank to 2/3 of capacity in 6 hours. How many hours will it take both pipes, pumping simultaneously at their respective constant rates, to fill the empty tank to capacity?  Pick one
A) 3.25  B) 3.6  C) 4.2  D) 4.4  E) 6
Time taken by First tank Fill 1/2 the tank = 9 hours   i.e. Time taken by First tank to Fill 1 complete the tank = 18 hours   Time taken by Second tank Fill 2/3 the tank = 6 hours   i.e. Time taken by First tank to Fill 1 complete the tank = (3/2)*6= 
<gadget id="calculator">(3/2)*6</gadget>
<output>9</output>
9 hours   in 1 Hour, Both tanks together Fill the tank= (1/18)+(1/9) =1/6 tank   i.e. Time taken by Both tank to Fill 1 complete the tank =6 hours   Answer: option 6
<result>E</result>
Pumping alone at their respective constant rates, one inlet pipe fills an empty tank to 1/2 of capacity in 9 hours and a second inlet pipe fills the same empty tank to 2/3 of capacity in 6 hours. How many hours will it take both pipes, pumping simultaneously at their respective constant rates, to fill the empty tank to capacity?