Number of days A required do a piece of work : 10
Number of days B required do a piece of work : 12
Number of days C required do a piece of work : 15
Work done by A in one day: \(\frac{1}{10}\)
Work done by C in one day: \(\frac{1}{12}\)
Work done by C in one day: \(\frac{1}{15}\)
Work done by A, B and C together in one day: \(\frac{1}{10}+\frac{1}{12}+\frac{1}{15}=\frac{15}{60}=\frac{1}{4}\)
∴ They can do the work together in 4 days .
