### BOATS AND STREAMS

This article explains how to solve boats and streams problems easily and quickly. The types of questions that can be expected from quantitative aptitude section of boats and streams include following

- You will be given the speed of boat in still water and the speed of stream. You have to find the time taken by boat to go upstream and downstream.
- You will be given the speed of boat to go up & down the stream, you will be asked to find speed of boat in still water and speed of stream
- You will be given speed of boat in up and down stream and will be asked to find the average speed of boat.
- You will be given the time taken by boat to reach a place in up and downstream and will be asked to find the distance to the place

The key point here is you can solve any of these questions using the formulas and short cuts given below.

Formulas and short cuts given below are also applicable to problems involving

**Cyclist and wind:**cyclist analogous to boat and wind analogous to stream**Swimmer and stream:**swimmer analogous to boat

#### General terms:

1) **Still water:** The water of a river or any other water body which is not flowing is known as still water.

2) **Stream:** It is the flowing water of a river which is moving at a certain speed.

3) **Upstream:** The boat or a swimmer moving against the stream is known as moving upstream i.e. against the flow of water.

4) **Downstream:** The boat or a swimmer moving along the stream is known as moving downstream i.e. along the flow of water.

## Points to remember:

1) If the speed of the boat or swimmer is X km/hr and the speed of the stream is Y km/hr,

The speed of the boat or swimmer in the direction of the stream is known as speed downstream. It is given by;

Speed downstream= (X+Y) km/hr

And, the speed of the boat or swimmer against the stream is known as speed upstream. It is given by;

Speed upstream= (X-Y) km/hr

2) Speed of man or boat in still water is given by;

= ( speed downstream + speed upstream)

3) Speed of the stream is given by;

= ( speed downstream – speed upstream)

4) A man can row at a speed of X km/hr in still water. If the speed of the stream is Y km/hr and the man rows the same distance up and down the stream, his average speed for the entire journey is given by;

=

= km/hr

5) A man can row a boat in still water at X km/hr. If the stream is flowing at Y km/hr it takes him t hours more to row upstream than to row downstream to cover the same distance. The distance is given by;

Distance =

6) A man can swim in still water at X km/hr. If the stream is flowing at Y km/hr it takes him t hours to reach a place and return back to the starting point. The distance between the place and the starting point is given by;

Distance =

7) A boat or swimmer covers a certain distance downstream in t1 hours and returns the same distance upstream in t2 hours. If the speed of the stream is Y km/hr, the speed of boat or man in still water is given by;

= Y km/hr

8) A boat or swimmer takes K times as long to move upstream as to move downstream to cover a certain distance. If the speed of the stream is Y km/hr, speed of the boat or man in still water is given by;

= Y km/hr