In this article, we will write a C program to calculate the average of 3 numbers using function. The program takes three numbers from the user as input, calculates their average and prints the result on the output window.

**Sample Example:**

```
Enter three numbers: 10 20 30
Average of 10, 20 and 30 is: 20.000000
Enter three numbers: 5 2 7
Average of 5, 2 and 7 is: 4.666667
```

To calculate the average of three numbers using a user-defined function, we have to create a function that takes the three numbers as argument, calculates their average and returns the result.

As the average of three numbers can be an integer or a float value, therefore, we will keep the return type of the function a `float`

which will take care of both integer and decimal point numbers. A `float`

value is nothing but a decimal point value.

See implementation in the following program:

// C program to find the average // of three numbers using a function #include <stdio.h> // Function declaration float average(int, int, int); int main() { int num1, num2, num3; float avg; printf("Enter three numbers: "); scanf("%d %d %d", &num1, &num2, &num3); // Get average using average() function avg = average(num1, num2, num3); printf("Average of %d, %d and %d is: %f", num1, num2, num3, avg); return 0; } // Function to calculate average of three numbers float average(int x, int y, int z){ float avg; avg = (x + y + z)/3.0; return avg; }

**Output:**

Enter three numbers: 20 30 40 Average of 20, 30 and 40 is: 30.000000 Enter three numbers: 10 11 11 Average of 10, 11 and 11 is: 10.666667

### Program Explanation:

- The program begins with the declaration of a function called
`average()`

, which takes three integer parameters (x, y, and z) and returns a floating-point value (avg). - This function is declared before the
`main()`

function to inform the compiler about its existence. - Variables
`num1`

,`num2`

, and`num3`

are used to store user-input numbers and a floating-point variable`avg`

to store the calculated average. - To calculate the average of the three input numbers, the
`average()`

function is called inside the main() function with the values of num1, num2, and num3 as arguments. - The result is stored in the
`avg`

variable. - Finally, the program uses
`printf()`

to display the calculated average along with the input values.

That’s all for this article. Thanks for reading!