Downstream: In water, the direction along the stream is called downstream.

If the speed of a boat in still water is u km/hr and the speed of the stream is v km/hr, then

Speed downstream = (u + v) km/hr

## What else you can do inside qs leap ?

Upstream: In water, the direction against the stream is called upstream.

Speed upstream = (u – v) km/hr

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Now, suppose if the speed downstream is already given as x km/hr and the speed upstream is given as y km/hr, then

Speed in still water = (x + y) / 2 km/hr

Speed of the stream = (x − y) / 2 km/hr

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Suppose a man swims at the speed of x km/hr in still water and he swims the same distance up and down in a stream which flows at a rate of y km/hr.

Then his average speed throughout the journey = (Speed downstream × Speed upstream) / (Speed in still water) = (x+y) * (x−y) / x

Solve the following question –

**A man rows 135 km upstream in 2.7 hours. He rows the same distance downstream in 2.5 hours. However for downstream, he reduces his speed by 9%, while speed of the current gets reduced by 20%. **

**Find the Speed of the man.**

*img credit: BBC*