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# Speed of boat in still water from speed of stream and times taken

• Last Updated : 15 Apr, 2021

Write a program to determine speed of the boat in still water(B) given the speed of the stream(S in km/hr), the time taken (for same point) by the boat upstream(T1 in hr) and downstream(T2 in hr).

Examples:

```Input : T1 = 4, T2 = 2, S = 5
Output : B = 15

Input : T1 = 6, T2 = 1, S = 7
Output : B = 9.8  ```

Prerequisite : Speed of boat upstream and downstream
Speed of boat in still water can be computed using below formula.
B = S*((T1 + T2) / (T1 – T2))

How does this formula work?
Since the point is same, distance traveled during upstream should be same as downstream.
Therefore,
(B – S) * T1 = (B + S) * T2
B(T1 – T2) = S*(T1 + T2)
B = S*(T1 + T2)/(T1 – T2)

## C++

 `// CPP program to find speed of boat in still water``// from speed of stream and times taken in downsteam``// and upstream``#include ``using` `namespace` `std;` `// Function to calculate the speed of boat in still water``float` `still_water_speed(``float` `S, ``float` `T1, ``float` `T2)``{``    ``return` `(S * (T1 + T2) / (T1 - T2));``}` `int` `main()``{``    ``float` `S = 7, T1 = 6, T2 = 1;``    ``cout << ``"The speed of boat in still water = "``<<``             ``still_water_speed(S, T1, T2)<<``" km/ hr "``;``    ``return` `0;``}`

## Java

 `// Java program to find speed of boat in still water``// from speed of stream and times taken in downsteam``// and upstream``import` `java.io.*;` `class` `GFG``{``    ``// Function to calculate the``    ``// speed of boat in still water``    ``static` `float` `still_water_speed(``float` `S, ``float` `T1, ``float` `T2)``    ``{``        ``return` `(S * (T1 + T2) / (T1 - T2));``    ``}` `    ``// Driver code``    ``public` `static` `void` `main (String[] args) {``        ``float` `S = ``7``, T1 = ``6``, T2 = ``1``;``        ``System.out.println(``"The speed of boat in still water = "``+``                            ``still_water_speed(S, T1, T2)+``" km/ hr "``);``    ` `    ``}``}` `// This code is contributed by vt_m.`

## Python3

 `# Python3 program to find speed of boat``# in still water from speed of stream and``# times taken in downsteam and upstream` `# Function to calculate the``# speed of boat in still water``def` `still_water_speed(S, T1, T2):``    ``return` `(S ``*` `(T1 ``+` `T2) ``/` `(T1 ``-` `T2))``    ` `# Driver code``S ``=` `7``; T1 ``=` `6``; T2 ``=` `1``print``(``"The speed of boat in still water = "``,``       ``still_water_speed(S, T1, T2), ``" km/ hr "``)``       ` `# This code is contributed by Anant Agarwal.`

## C#

 `// C# program to find speed of boat``// in still water from speed of stream``// and times taken in downsteam``// and upstream``using` `System;` `class` `GFG {``    ` `    ``// Function to calculate the``    ``// speed of boat in still water``    ``static` `float` `still_water_speed(``float` `S, ``float` `T1,``                                            ``float` `T2)``    ``{``        ``return` `(S * (T1 + T2) / (T1 - T2));``    ``}` `    ``// Driver code``    ``public` `static` `void` `Main()``    ``{``        ``float` `S = 7, T1 = 6, T2 = 1;``        ``Console.WriteLine(``"The speed of boat in still water = "` `+``                      ``still_water_speed(S, T1, T2) + ``" km/ hr "``);``    ``}``}` `// This code is contributed by vt_m.`

## PHP

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## Javascript

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Output:

`The speed of boat in still water = 9.8 km/hr`

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