Downstream/Upstream :
In water, the direction along the stream is called downstream.
And, the direction against the stream is called upstream.
Important Formulae :
If the speed of a boat in still water is u kmph and the speed of the stream is v kmph, then :
Speed downstream = (u + v) kmph.
Speed upstream = (u − v) kmph.
If the speed downstream is a kmph and the speed upstream is b kmph, then :
Speed in still water = 1 2 (a + b) kmph.
Rate of stream = 1 2 (a − b) kmph.