Pumping alone at their respective constant rates, one inlet pipe fills an empty tank to 1/2 of capacity in 6 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?  Choose the correct choice:
A) 3.25 B) 3.6 C) 4.2 D) 4.4 E) 5.14
Time taken by First tank Fill 1/2 the tank = 6 hours   i.e. Time taken by First tank to Fill 1 complete the tank =12 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= (1/12)+(1/9) = 7/36 tank   i.e. Time taken by Both tank to Fill 1 complete the tank = 36/7 hours = 5.14 hours   Answer: option 5.14
<result>E</result>
Pumping alone at their respective constant rates, one inlet pipe fills an empty tank to 1/2 of capacity in 6 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?