A & B complete work in 24 days and 30 days respectively working 10 hours a day.In a day there are two shifts morning for 6 Hours and evening for 4 Hours.on first day A works in morning and B works in evening then next day shift changes and they work end so on.so find the day when work is completed.
dhyan se dekhe to altenate days pe dono ka 1 day work ho raha hain. I mean in 2 days A does his 1 day work whereas in the same two days b does his 1 day work. so forget the hours and do the answer normally. so if we take lcm we get 120 units of work. and A does 5units of work where as B does 4 units of work. until the 26th day 117 units of work are done. rest 3 units of work will be done on the 27th day by A. so 27 is the answer. I am just applying the logic. I may be wrong. But this is the best explanation i could think of.