# Length of rope tied around three equal circles touching each other

• Last Updated : 07 Jul, 2022

Given r is the radius of three equal circles touching each other. The task is to find the length of the rope tied around the circles as shown below: Examples:

Input: r = 7
Output: 86

Input: r = 14
Output: 172

Approach: As it can be clearly seen from above image, the part of the length of rope which is not touching the circle is 2r + 2r + 2r = 6r
The part of the rope which is touching the circles make a sector of 120 degrees on each circle. Thus, three sectors of 120 degrees each can be considered as a complete one circle of 360 degrees.
Therefore, Length of rope touching the circle is 2 * PI * r where PI = 22 / 7 and r is the radius of the circle.
Hence, the total length of the rope will be ( 2 * PI * r ) + 6r.

Below is the implementation of the above approach:

## C++

 `// C++ program to find the length``// of rope``#include``using` `namespace` `std;``#define PI 3.14159265` `// Function to find the length``// of rope``float` `length_rope( ``float` `r )``{``    ``return` `( ( 2 * PI * r ) + 6 * r );``}` `// Driver code``int` `main()``{``    ``float` `r = 7;``    ``cout<<``ceil``(length_rope( r ))<

## C

 `// C program to find the length``// of rope``#include ``#define PI 3.14159265` `// Function to find the length``// of rope``float` `length_rope( ``float` `r )``{``    ``return` `( ( 2 * PI * r ) + 6 * r );``}` `// Driver code``int` `main()``{``    ``float` `r = 7;``    ``printf``(``"%f"``,``           ``length_rope( r ));``    ``return` `0;``}`

## Java

 `// Java code to find the length``// of rope``import` `java.lang.*;` `class` `GFG {` `    ``static` `double` `PI = ``3.14159265``;` `    ``// Function to find the length``    ``// of rope``    ``public` `static` `double` `length_rope(``double` `r)``    ``{``        ``return` `((``2` `* PI * r) + ``6` `* r);``    ``}` `    ``// Driver code``    ``public` `static` `void` `main(String[] args)``    ``{``        ``double` `r = ``7``;``        ``System.out.println(length_rope(r));``    ``}``}`

## Python3

 `# Python3 code to find the length``# of rope``PI ``=` `3.14159265``    ` `# Function to find the length``# of rope``def` `length_rope( r ):``    ``return` `( ( ``2` `*` `PI ``*` `r ) ``+` `6` `*` `r )``    ` `# Driver code``r ``=` `7``print``( length_rope( r ))`

## C#

 `// C# code to find the length``// of rope``using` `System;` `class` `GFG {``    ``static` `double` `PI = 3.14159265;` `    ``// Function to find the length``    ``// of rope``    ``public` `static` `double` `length_rope(``double` `r)``    ``{``        ``return` `((2 * PI * r) + 6 * r);``    ``}` `    ``// Driver code``    ``public` `static` `void` `Main()``    ``{``        ``double` `r = 7.0;``        ``Console.Write(length_rope(r));``    ``}``}`

## PHP

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## Javascript

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Output:

`86`

Time Complexity: O(1)

Auxiliary Space: O(1)

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