Four buses run between Bhopal and Gwalior. If a man goes from Gwalior to Bhopal by a bus and comes back to Gwalior by another bus, find the total possible ways.

The streets of a city are arranged like the lines of a chess board. There are m streets running from north to south and n streets from east to west. Find the number of ways in which a man can travel from north-west to south-east corner, covering shortest possible distance.

From roof of a multi storeyed building a man saw a running bus came straight towards the building. If the angle of depression in 6 minutes raise from 30^@ and 60^@ , then when the bus will come at the foot of the building?