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

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
```

## Recommended: Please try your approach on {IDE} first, before moving on to the solution.

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

 ` `

Output:

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

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