Joe can clean the house in 4 hours. Cindy can clean the house in 3 hours. How many hours will it take for both of them working together to clean the house?	Choose the correct choice from the following answers:
A) 1 B) 2 5/7 C) 2 1/5 D) 1 5/7 E) 3 1/2
Work hrs=AB/(A+B)= 12/7 =1 5/7   Answer is 1 5/7
<result>D</result>
Joe can clean the house in 4 hours. Cindy can clean the house in 3 hours. How many hours will it take for both of them working together to clean the house?