If A can do a piece of work in p days and B can do the same in q days: A and B together can finish it in how many days

A can do a piece of work in 10 days, B can do it in 15 days working together they can finish the work in :

A and B can do a piece of work in 9 days; B and C can do it in 12 days; A and C can do it in 18 days.In how many days will A,B and C finish it working together and separately?

A and B together can do a piece of work in 36 days, B and C together can do it in 24 days. A and C together can do it in 18 days. The three working together can finish the work in

A and B can do a piece of work in 72 days B and C can do it in 120 days. A and C can do it in 90 days. In how many days, all the three together can do the work?

A can do a piece of work in 24 days, A and B can do it in 16 days and A,B and C in 10(2)/(3) days. In how many days can A and C do it working together ?

A and B together can do a piece of work in 5 days and A alone can do it in 30 days. B alone can do the work in how many days?