The ratio of efficiences of A, B and C is 1 : 3 : 5. Working together they can complete 60% of the work in 20 days. Find out how much time will it take by A and B to complete the remaining work.

30 days

60% of the work = efficiency x days = 9 x 20 = 180

100% of the work = \(\frac{100}{60}\) x 180 = 300

remaining work = 300 - 180 = 120

time taken by A and B to complete the work = \(\frac{Total\; work}{Efficiency}\)

                                                                = \(\frac{120}{4}\) = 30 days