X, Y and Z can complete a piece of work in 10 days. X and Y can do it in 20 days. Then Z alone can complete the work in ……………… days.

A and B can do a piece of work in 10 days, B and C in 15 days and C and A in 20 days. C alone can do the work in :

U, V and W together can complete a work in 10 days. If U alone can complete the work in 20 days and V alone can complete the work in 30 days, then in how many days W alone can complete the work?

X and Y contracted a piece of work for Rs. 1600. X alone can do it in 6 days, while Y alone can do that work in 8 days. They completed the work in 3 days taking help of A. Find the share of A.

Working together, X and Y can do a piece of work in 12 days, Y and Z can do it in 15 days where as X and Z can do it in 20 days. Who is the most effcient?