‘A’ can complete 50% of a work in 6 days. ‘B’ takes 4 days more than ‘A’ to complete the work and ‘B’ is 25% more efficient than ‘C’. ‘A’ started the work alone; on the 2nd day, he is joined by ‘B’ only; on the 3rd day, he is joined by ‘C’ only; on the 4th day, he works alone again, and so on. They worked this way for 6 days. The sum of the time taken to complete the remaining work by ‘A’ alone and by ‘B’ alone is how much percent more/less than that by ‘C’ alone? 

Time taken by ‘A’ to complete the work alone: = 6 / 0.5 = 12 days Time taken by ‘B’ to complete the work alone: = 12 + 4 = 16 days Time taken by ‘C’ to complete the work alone: = 16 × 1.25 = 20 days Total Work (LCM of 12, 16, 20): = 240 units Efficiency of ‘A’: = 240 / 12 = 20 units/day Efficiency of ‘B’: = 240 / 16 = 15 units/day Efficiency of ‘C’: = 240 / 20 = 12 units/day Work done on Day 1 (A alone): = 20 units Work done on Day 2 (A + B): = 20 + 15 = 35 units Work done on Day 3 (A + C): = 20 + 12 = 32 units Work done in 3 days (1 cycle): = 20 + 35 + 32 = 87 units Work done in 6 days (2 cycles): = 87 × 2 = 174 units Remaining work: = 240 – 174 = 66 units Time taken by ‘A’ to complete remaining work alone: = 66 / 20 = 3.3 days Time taken by ‘B’ to complete remaining work alone: = 66 / 15 = 4.4 days Time taken by ‘C’ to complete remaining work alone: = 66 / 12 = 5.5 days Sum of time taken by ‘A’ and ‘B’ alone: = 3.3 + 4.4 = 7.7 days Required percentage: = [ (7.7 – 5.5) / 5.5 ] × 100 = (2.2 / 5.5) × 100 = 40% more