A larger hose connected to a swimming pool can fill the pool in 6 hours. A smaller hose can fill the pool in 12 hours. How many hours will it take for both of them to fill the pool? Choose one
A) 3  B) 7 1/2  C) 5 3/5  D) 8  E) 4
Work hrs=AB/(A+B)= 72/18= 
<gadget id="calculator">72/18</gadget>
<output>4</output>
4   Answer is 4
<result>E</result>
A larger hose connected to a swimming pool can fill the pool in 6 hours. A smaller hose can fill the pool in 12 hours. How many hours will it take for both of them to fill the pool?