# Quantitative Aptitude - Boats and Streams - Formula & Concept Tutorial

**Downstream**-

In water , the direction along the stream is called **downstream**.

**Upstream**–

In water , the direction against the stream is called **upstream**.

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

**a** = Speed downstream = ( u + v ) km/hr = u + v

**b** = Speed upstream = ( u – v ) km/hr = u – v

- If the speed downstream is
**a**km/hr and speed upstream is b km/hr then

**u** = Speed in still water =

**v** = Rate of stream =

- Suppose a boat cover a certain distance at
**x**km/hr and an equal distance at**y**km/hr the boat reverse.

Then the average speed during the whole journey is