**Stream: **Moving water of the river is called stream.

**Still Water:** If the water is not moving then it is called still water.

**Upstream:** If a boat or a swimmer moves in the opposite direction of the stream then it is called upstream.

**Downstream:** If a boat or a swimmer moves in the same direction of the stream then it is called downstream.

**Points to remember**

- When speed of boat or a swimmer is given then it normally means speed in still water.

## Basic Formulas of Boats and Streams

**Rule 1:** If speed of boat or swimmer is x km/h and the speed of stream is y km/h then,

- Speed of boat or swimmer upstream = (x − y) km/h
- Speed of boat or swimmer downstream = (x + y) km/h

**Rule 2:**

- Speed of boat or swimmer in still water is given by

- Speed of stream is given by

## Shortcut methods for Boats and Streams

**Rule 1:** A man can row certain distance downstream in t_{1} hours and returns the same distance upstream in t_{2} hours. If the speed of stream is y km/h, then the speed of man in still water is given by

**Rule 2:** A man can row in still water at x km/h. In a stream flowing at y km/h, if it takes him t hours to row to a place and come back, then the distance between two places is given by

**Rule 3:** A man can row in still water at x km/h. In a stream flowing at y km/h, if it takes t hours more in upstream than to go downstream for the same distance, then the distance is given by

**Rule 4:** A man can row in still water at x km/h. In a stream flowing at y km/h, if he rows the same distance up and down the stream, then his average speed is given by