The college auditorium is to be painted. But due to lack of funds it couldn’t be done. So a sincere student took the initiative and decided to paint the audi. Seeing his enthusiasm other students joined him. He is the only person doing the job on the first day. On the second day 2 more boys join him. On the third day 3 more boys join the group of the previous day and so on.....In this manner, the job is finished in exactly 25 days. How many days would 15 workers take to do the same job, given that one man is twice as efficient as a boy.