Arithmetic Questions And Answers :: Time And Work: part1

6.A and B can do a piece of work in 18 days; B can C in 24 days; A and C in 36 days. In what time can they do it all working together?

7.A and B can together finish a work in 30 days. They worked for it for 20 days and then B left. The remaining work was done by A alone in 20 more days. A alone can finish the work in:

8.A can do a piece of work in 10 days and B can do the same piece of work in 20 days. They start the work together but after 5 days. A leaves off. B will do the remaining piece of work in:

9.A can do a piece of work in 80 days. He works at it for 10 days and then B alone finishes the work in 42 days. The two together could complete the work in:

10.A can do (1/3) of a work in 5 days and B can do (2/5) of the work in 10 days. In how many days both A and B together can do the work ?