Question
A river d km wide is flowing at a rate 
A swimmer which can swim with velocity 
relative to water, dives into the river perpendicular to the direction of flow to cross the river. How far he will go down the river along the river?
Solution
When the swimmer dives perpendicular to river, then time taken by swimmer to cross the river is,
The distance which the swimmer will go down the river along the river is,
The distance which the swimmer will go down the river along the river is,
