Given two concentric circles with radius **X** and **Y** where (**X > Y**). Find the area between them.

You are required to find the area of the green region as shown in the following image:

**Examples:**

Input :X = 2, Y = 1Output :9.42478Input :X = 4, Y = 2Output :37.6991

**Approach:**

The area between the two given concentric circles can be calculated by subtracting the area of the inner circle from the area of the outer circle. Since **X>Y**. **X** is the radius of the outer circle.

Therefore, area between the two given concentric circles will be:

π*X^{2}- π*Y^{2}

Below is the implementation of the above approach:

## C++

`// C++ program to find area between the` `// two given concentric circles` `#include <bits/stdc++.h>` `using` `namespace` `std;` `// Function to find area between the` `// two given concentric circles` `double` `calculateArea(` `int` `x, ` `int` `y)` `{` ` ` `// Declare value of pi` ` ` `double` `pi = 3.1415926536;` ` ` `// Calculate area of outer circle` ` ` `double` `arx = pi * x * x;` ` ` `// Calculate area of inner circle` ` ` `double` `ary = pi * y * y;` ` ` `// Difference in areas` ` ` `return` `arx - ary;` `}` `// Driver Program` `int` `main()` `{` ` ` `int` `x = 2;` ` ` `int` `y = 1;` ` ` `cout << calculateArea(x, y);` ` ` `return` `0;` `}` |

## Java

`// Java program to find area between the` `// two given concentric circles` `import` `java.io.*;` `class` `GFG` `{` ` ` `// Function to find area between the` `// two given concentric circles` `static` `double` `calculateArea(` `int` `x, ` `int` `y)` `{` ` ` `// Declare value of pi` ` ` `double` `pi = ` `3.1415926536` `;` ` ` `// Calculate area of outer circle` ` ` `double` `arx = pi * x * x;` ` ` `// Calculate area of inner circle` ` ` `double` `ary = pi * y * y;` ` ` `// Difference in areas` ` ` `return` `arx - ary;` `}` `// Driver code` `public` `static` `void` `main (String[] args)` `{` ` ` `int` `x = ` `2` `;` ` ` `int` `y = ` `1` `;` ` ` `System.out.println (calculateArea(x, y));` `}` `}` `// This code is contributed by jit_t.` |

## Python3

`# Python3 program to find area between ` `# the two given concentric circles` `# Function to find area between the` `# two given concentric circles` `def` `calculateArea(x, y):` ` ` `# Declare value of pi` ` ` `pi ` `=` `3.1415926536` ` ` `# Calculate area of outer circle` ` ` `arx ` `=` `pi ` `*` `x ` `*` `x` ` ` `# Calculate area of inner circle` ` ` `ary ` `=` `pi ` `*` `y ` `*` `y` ` ` `# Difference in areas` ` ` `return` `arx ` `-` `ary` `# Driver Code` `x ` `=` `2` `y ` `=` `1` `print` `(calculateArea(x, y))` `# This code is contributed` `# by shashank_sharma` |

## C#

`// C# program to find area between the` `// two given concentric circles` `using` `System;` `class` `GFG` `{` ` ` `// Function to find area between the` `// two given concentric circles` `static` `double` `calculateArea(` `int` `x, ` `int` `y)` `{` ` ` `// Declare value of pi` ` ` `double` `pi = 3.1415926536;` ` ` `// Calculate area of outer circle` ` ` `double` `arx = pi * x * x;` ` ` `// Calculate area of inner circle` ` ` `double` `ary = pi * y * y;` ` ` `// Difference in areas` ` ` `return` `arx - ary;` `}` `// Driver code` `public` `static` `void` `Main ()` `{` ` ` `int` `x = 2;` ` ` `int` `y = 1;` ` ` `Console.WriteLine(calculateArea(x, y));` `}` `}` `// This code is contributed by Code_Mech.` |

## PHP

`<?php` `// PHP program to find area between the` `// two given concentric circles` `// Function to find area between the` `// two given concentric circles` `function` `calculateArea(` `$x` `, ` `$y` `)` `{` ` ` `// Declare value of pi` ` ` `$pi` `= 3.1415926536;` ` ` `// Calculate area of outer circle` ` ` `$arx` `= ` `$pi` `* ` `$x` `* ` `$x` `;` ` ` `// Calculate area of inner circle` ` ` `$ary` `= ` `$pi` `* ` `$y` `* ` `$y` `;` ` ` `// Difference in areas` ` ` `return` `(` `$arx` `- ` `$ary` `);` `}` `// Driver Code` `$x` `= 2;` `$y` `= 1;` `echo` `calculateArea(` `$x` `, ` `$y` `);` `// This code is contributed by akt_mit` `?>` |

## Javascript

`<script>` `// Javascript program to find area between` `// the two given concentric circles` `// Function to find` `// nth concentric hexagon number` `function` `calculateArea(x, y)` `{` ` ` ` ` `// Declare value of pi` ` ` `var` `pi = 3.1415926536;` ` ` `// Calculate area of outer circle` ` ` `var` `arx = pi * x * x;` ` ` `// Calculate area of inner circle` ` ` `var` `ary = pi * y * y;` ` ` ` ` `// Difference in areas` ` ` `return` `arx - ary;` `}` `// Driver code` `var` `x = 2;` `var` `y = 1;` ` ` `// Function call` `document.write(calculateArea(x, y));` `// This code is contributed by Ankita saini` `</script>` |

**Output:**

9.42478

**Time Complexity:** O(1)

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