A and B together can complete a piece of work in 36 days while A and C together can complete the same work in 39 days. If A, B, and C together can complete 75% of the work in 19.5 days then find the time taken by B and C together to complete 77% of the whole work.

Total time taken by A, B, and C to complete. the whole work = 19.5/0.75 = 26 days Let the total amount of work = 468 units (LCM of 36, 39 and 26) Efficiency of A and B together = 468/36 = 13 units per day Efficiency of A and C together = 468/39 = 12 units per day Efficiency of A, B, and C together = 468/26 = 18 units per day Efficiency of A = 13 + 12 – 18 = 7 units per days efficiency of B=18-12=6days efficiency of C=18-13=5days Then the efficiency of B+C= 6+5=11days Required time taken of B+C= (468×.77)/11 =32.76days