# Boats & Stream

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 t1 hours and returns the same distance upstream in t2 hours. If the speed of stream is y km/h, then the speed of man in still water is given by

Example

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

Example

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

Example

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

Example