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Average of odd numbers till a given odd number
• Last Updated : 24 Mar, 2021

Given an odd number n, find the average of odd numbers from 1 to n.
Examples:

```Input : n = 9
Output : 5
Explanation
(1 + 3 + 5 + 7 + 9)/5
= 25/5
= 5

Input : n = 221
Output : 111```

Method 1 We can calculate average by adding each odd numbers till n and then dividing sum by count.
Below is the implementation of the approach.

## C++

 `// Program to find average of odd numbers``// till a given odd number.``#include ` `// Function to calculate the average``// of odd numbers``int` `averageOdd(``int` `n)``{``    ``if` `(n % 2 == 0) {``        ``printf``(``"Invalid Input"``);``        ``return` `-1;``    ``}` `    ``int` `sum = 0, count = 0;``    ``while` `(n >= 1) {` `        ``// count odd numbers``        ``count++;` `        ``// store the sum of odd numbers``        ``sum += n;` `        ``n = n - 2;``    ``}``    ``return` `sum / count;``}` `// driver function``int` `main()``{``    ``int` `n = 15;``    ``printf``(``"%d"``, averageOdd(n));``    ``return` `0;``}`

## Java

 `// Program to find average of odd numbers``// till a given odd number.``import` `java.io.*;` `class` `GFG {``    ` `    ``// Function to calculate the average``    ``// of odd numbers``    ``static` `int` `averageOdd(``int` `n)``    ``{``        ``if` `(n % ``2` `== ``0``) {``            ``System.out.println(``"Invalid Input"``);``            ``return` `-``1``;``        ``}``     ` `        ``int` `sum = ``0``, count = ``0``;``        ``while` `(n >= ``1``) {``     ` `            ``// count odd numbers``            ``count++;``     ` `            ``// store the sum of odd numbers``            ``sum += n;``     ` `            ``n = n - ``2``;``        ``}``        ``return` `sum / count;``    ``}``     ` `    ``// driver function``    ``public` `static` `void` `main(String args[])``    ``{``        ``int` `n = ``15``;``        ``System.out.println(averageOdd(n));``    ``}``}` `/*This code is contributed by Nikita tiwari.*/`

## Python3

 `# Program to find average``# of odd numbers till a``# given odd number.` `# Function to calculate``# the average of odd``# numbers``def` `averageOdd(n) :` `    ``if` `(n ``%` `2` `=``=` `0``) :``        ``print``(``"Invalid Input"``)``        ``return` `-``1``    ` `    ``sm ``=` `0``    ``count ``=` `0` `    ``while` `(n >``=` `1``) :` `        ``# count odd numbers``        ``count ``=` `count ``+` `1` `        ``# store the sum of``        ``# odd numbers``        ``sm ``=` `sm ``+` `n` `        ``n ``=` `n ``-` `2``    ` `    ``return` `sm ``/``/` `count``    ` `# Driver function``n ``=` `15``print``(averageOdd(n))` `# This code is contributed by Nikita Tiwari.`

## C#

 `// C# Program to find average ``// of odd numbers till a given``// odd number.``using` `System;` `class` `GFG {``    ` `    ``// Function to calculate the``    ``// average of odd numbers``    ``static` `int` `averageOdd(``int` `n)``    ``{``        ``if` `(n % 2 == 0) {``            ``Console.Write(``"Invalid Input"``);``            ``return` `-1;``        ``}``    ` `        ``int` `sum = 0, count = 0;``        ``while` `(n >= 1) {``    ` `            ``// count odd numbers``            ``count++;``    ` `            ``// store the sum of odd numbers``            ``sum += n;``    ` `            ``n = n - 2;``        ``}``        ``return` `sum / count;``    ``}``    ` `    ``// driver function``    ``public` `static` `void` `Main()``    ``{``        ``int` `n = 15;``        ``Console.Write(averageOdd(n));``    ``}``}` `/*This code is contributed by vt_m.*/`

## PHP

 `= 1)``    ``{` `        ``// count odd numbers``        ``\$count``++;` `        ``// store the sum of``        ``// odd numbers``        ``\$sum` `+= ``\$n``;` `        ``\$n` `= ``\$n` `- 2;``    ``}``    ``return` `\$sum` `/ ``\$count``;``}` `    ``// Driver Code``    ``\$n` `= 15;``    ``echo``(averageOdd(``\$n``));``    ` `// This code is contributed by vt_m.``?>`

## Javascript

 ``

Output:

`8`

Method 2
The average of odd numbers can find out only in single steps
by using the following formula
[n + 1 ] / 2
where n is last odd number.
How does this formula work?

```We know there are (n+1)/2 odd numbers till n.

For example:
There are two odd numbers till 3 and there are
three odd numbers till 5.

Sum of first k odd numbers is k*k

Sum of odd numbers till n is ((n+1)/2)2

Average of odd numbers till n is (n + 1)/2```

Below is the implementation of the approach.

## C

 `// Program to find average of odd numbers``// till a given odd number.``#include ` `// Function to calculate the average``// of odd numbers``int` `averageOdd(``int` `n)``{``    ``if` `(n % 2 == 0) {``        ``printf``(``"Invalid Input"``);``        ``return` `-1;``    ``}` `    ``return` `(n + 1) / 2;``}` `// driver function``int` `main()``{``    ``int` `n = 15;``    ``printf``(``"%d"``, averageOdd(n));``    ``return` `0;``}`

## Java

 `// Program to find average of odd``// numbers till a given odd number.``import` `java.io.*;` `class` `GFG``{``    ``// Function to calculate the``    ``// average of odd numbers``    ``static` `int` `averageOdd(``int` `n)``    ``{``        ``if` `(n % ``2` `== ``0``)``        ``{``            ``System.out.println(``"Invalid Input"``);``            ``return` `-``1``;``        ``}``    ` `        ``return` `(n + ``1``) / ``2``;``    ``}``    ` `    ``// driver function``    ``public` `static` `void` `main(String args[])``    ``{``        ``int` `n = ``15``;``        ``System.out.println(averageOdd(n));``    ``}``}` `// This code is contributed by Nikita tiwari.`

## Python3

 `# Program to find average of odd``# numbers till a given odd number.` `# Function to calculate the``# average of odd numbers``def` `averageOdd(n) :``    ``if` `(n ``%` `2` `=``=` `0``) :``        ``print``(``"Invalid Input"``)``        ``return` `-``1``    ` `    ` `    ``return` `(n ``+` `1``) ``/``/` `2``    ` `# driver function``n ``=` `15``print``(averageOdd(n))`   `# This code is contributed by Nikita tiwari.`

## C#

 `// C# Program to find average``// of odd numbers till a given``// odd number.``using` `System;` `class` `GFG``{``    ``// Function to calculate the``    ``// average of odd numbers``    ``static` `int` `averageOdd(``int` `n)``    ``{``        ``if` `(n % 2 == 0)``        ``{``            ``Console.Write(``"Invalid Input"``);``            ``return` `-1;``        ``}``    ` `        ``return` `(n + 1) / 2;``    ``}``    ` `    ``// driver function``    ``public` `static` `void` `Main()``    ``{``        ``int` `n = 15;``        ``Console.Write(averageOdd(n));``    ``}``}` `// This code is contributed by vt_m.`

## PHP

 ``

## Javascript

 ``

Output:

`8`

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