Let the total work be 234 units. {LCM (13 and 18)} So, efficiency of ‘A’ = (234/13) = 18 units/day So, efficiency of ‘B’ = (18 x 0.5) = 9 unit/day Efficiency of ‘B’ and ‘C’ together = (234/18) = 13 units/day So, efficiency of ‘C’ = 13 – 9 = 4 units/day So, time taken by ‘C’ to finish the work alone = (234/4) = 58.5 days