A can do a piece of work in 10 days while B alone can do it in 15 days. In how many days can both finish the same work?

Number of days A required do a piece of work : 10

Number of days B required do a piece of work : 15

Work done by A in one day:

Work done by B in one day:

Work done by A and B together in one day: = =

They can do the work together in 6 days.