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: \(\frac{1}{10}\)
Work done by B in one day: \(\frac{1}{15}\)
Work done by A and B together in one day: \(\frac{1}{10}+\frac{1}{15}=\frac{5}{30}=\frac{1}{6}\)
∴ They can do the work together in 6 days.