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Program to find the rate percentage from compound interest of consecutive years
• Last Updated : 28 May, 2019

Given two integers N1 and N2 which is the Compound Interest of two consecutive years. The task is to calculate the rate percentage.

Examples:

Input: N1 = 660, N2 = 720
Output: 9.09091 %

Input: N1 = 100, N2 = 120
Output: 20 %

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

Approach: The rate percentage can be calculated with the formula ((N2 – N1) * 100) / N1 where N1 is the compound interest of some year and N2 is the compound interest for the next year.

Let us consider the 1st Example:
The difference between the Compound interest in the two consecutive years is because of the interest received on the previous year interest. Therefore,
–> N2 – N1 = N1 * (Rate / 100)
–> 720 – 660 = 660 * (Rate / 100)
–> (60 / 660) * 100 = Rate
–> Rate = (100 / 11) = 9.09% (Approx)

Below is the implementation of the above approach:

## C++

 `// C++ implementation of the approach ` `#include ` `using` `namespace` `std; ` ` `  `// Function to return the ` `// required rate percentage ` `float` `Rate(``int` `N1, ``int` `N2) ` `{ ` `    ``float` `rate = (N2 - N1) * 100 / ``float``(N1); ` ` `  `    ``return` `rate; ` `} ` ` `  `// Driver code ` `int` `main() ` `{ ` `    ``int` `N1 = 100, N2 = 120; ` ` `  `    ``cout << Rate(N1, N2) << ``" %"``; ` ` `  `    ``return` `0; ` `} `

## Java

 `// Java implementation of the approach ` ` `  `class` `GFG  ` `{ ` ` `  `    ``// Function to return the ` `    ``// required rate percentage ` `    ``static` `int` `Rate(``int` `N1, ``int` `N2) ` `    ``{ ` `        ``float` `rate = (N2 - N1) * ``100` `/ N1; ` ` `  `        ``return` `(``int``)rate; ` `    ``} ` ` `  `    ``// Driver code ` `    ``public` `static` `void` `main(String[] args)  ` `    ``{ ` `        ``int` `N1 = ``100``, N2 = ``120``; ` ` `  `        ``System.out.println(Rate(N1, N2) + ``" %"``); ` `    ``} ` `} ` ` `  `// This code has been contributed by 29AjayKumar `

## Python 3

 `# Python 3 implementation of the approach ` ` `  `# Function to return the ` `# required rate percentage ` `def` `Rate( N1, N2): ` `    ``rate ``=` `(N2 ``-` `N1) ``*` `100` `/``/` `(N1); ` ` `  `    ``return` `rate ` ` `  `# Driver code ` `if` `__name__ ``=``=` `"__main__"``: ` `    ``N1 ``=` `100` `    ``N2 ``=` `120` ` `  `    ``print``(Rate(N1, N2) ,``" %"``) ` ` `  `# This code is contributed by ChitraNayal     `

## C#

 `// C# implementation of the approach ` `using` `System; ` ` `  `class` `GFG ` `{ ` `     `  `    ``// Function to return the ` `    ``// required rate percentage ` `    ``static` `int` `Rate(``int` `N1, ``int` `N2) ` `    ``{ ` `        ``float` `rate = (N2 - N1) * 100 / N1; ` ` `  `        ``return` `(``int``)rate; ` `    ``} ` ` `  `    ``// Driver code ` `    ``static` `public` `void` `Main () ` `    ``{ ` `        ``int` `N1 = 100, N2 = 120; ` ` `  `        ``Console.WriteLine(Rate(N1, N2) + ``" %"``); ` `    ``} ` `} ` ` `  `// This code has been contributed by ajit. `

## PHP

 ` `

Output:

```20 %
```

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