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# Program to find the rate percentage from compound interest of consecutive years

• Difficulty Level : Basic
• Last Updated : 01 Apr, 2021

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 %

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 percentagefloat Rate(int N1, int N2){    float rate = (N2 - N1) * 100 / float(N1);     return rate;} // Driver codeint 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 percentagedef Rate( N1, N2):    rate = (N2 - N1) * 100 // (N1);     return rate # Driver codeif __name__ == "__main__":    N1 = 100    N2 = 120     print(Rate(N1, N2) ," %") # This code is contributed by ChitraNayal

## C#

 // C# implementation of the approachusing 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.



## Javascript


Output:
20 %

Time Complexity: O(1)

Auxiliary Space: O(1)

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