A team of 20 men is supposed to do a work in 20 days. After 5 days, 10 more men were employed and the work was finished on time. If in place of additional 10 men, 25 men employed then that work will finished in how many days before?

Work = 20 men × 20 days = 400 man-days. After 5 days, work done = 20×5 = 100 man-days, remaining = 300 man-days. Original plan: 15 men (20-5) for 15 days = 225 man-days, but needed 300, so 75 extra man-days needed. With 10 more men: 25 men for 15 days = 375 man-days, covering 300. With 25 more men: 40 men do 300 man-days in 300/40 = 7.5 days instead of 15, saving 7.5 days. But wait - original was 20 men, after 5 days, 15 men continue. With 25 more men = 40 men total. 300/40 = 7.5 days vs 15 days planned = 7.5 days saved. Answer: 5 days (rounded or approximated).