458. A man is waiting for a bus on routes 10, 17 and 25. The bus on route 10 comes every 10 min, bus on route 17 comes every 20 min, and bus on route 25 comes every 40 min. After the man reaches the stop, a bus just leaves the stop. What is the minimum time for which he has to wait to get a bus?
Examination: UPSC Prelims 1989