Number of days A required do a piece of work : 20
Number of days B required do a piece of work : 12
Work done by A in one day: \(\frac{1}{20}\)
Work done by B in one day: \(\frac{1}{12}\)
B works alone for 9 days, so work completed by B in 9 days : \(9\times\frac{1}{12}=\frac{3}{4}\)
Work left = \(1-\frac{3}{4}=\frac{1}{4}\)
But \(\frac{3}{4}\)th of the work is already done by B
∴ Time required to complete the remaining \(\frac{1}{4}\)th of the work by A : \(\frac{1}{4}\times20\) = 5 days
∴ Time taken to finish the work 9 + 5 = 14 days
∴ A can finish the remaining work in : 5 days
