A man covered a distance of 2000 km in 18 hrs partly by bus at 72 kmph and partly by train at 160 kmph. The distance covered by the bus is:

1) 1280 km
2) 720 km
3) 860 km
4) 640 km
5) 320 km

Its clear that, the answer should be 72*5 or 72*10 or 72*15

Try,

a)72*5 = 360 , remaining (2000-360) = 1640 (cannot be the distance by train)
b)72*10 = 720, remaining (2000-720) = 1280 (takes 8 hrs for train) - success!!

IMO: 2