24 boys will complete a piece of work in 18 days. 2 days after they started the work, 8 more boys joined with them. In how many days will all of them together finish the leftover work?
After 2 days boys have 1/9 of a job done, so 8/9 was left. Their speed increased by 1/3, becoming 4/3 of the initial speed of work. Initial group would have finished the job in 16 days, larger group would finish in 3/4 of the time, that is 12 days.