Average of 3 Numbers in C++

Average of 3 Numbers in C++ (4 Programs).

BeginnerArray Operations ProgramsExample 4 of 7

average-of-3-numbers.cpp

1#include <iostream>
2#include <iomanip>
3using namespace std;
4
5int main() {
6    float num1, num2, num3;
7    
8    cout << "Enter three numbers: ";
9    cin >> num1 >> num2 >> num3;
10    
11    float average = (num1 + num2 + num3) / 3.0;
12    
13    cout << fixed << setprecision(2);
14    cout << "Average of " << num1 << ", " << num2 << ", and " << num3 
15         << " = " << average << endl;
16    
17    return 0;
18}

Output

Enter three numbers: 10 20 30
Average of 10.00, 20.00, and 30.00 = 20.00

What's going on

The program calculates the average of three numbers. For example:

Input: 10, 20, 30

Calculation: (10 + 20 + 30) / 3 = 60 / 3 = 20

Output: 20.00

The average represents the central value of a set of numbers, providing a single value that summarizes the data.

Example:

Numbers: 5, 10, 15 → Average: (5 + 10 + 15) / 3 = 10

Numbers: 7.5, 8.5, 9.5 → Average: (7.5 + 8.5 + 9.5) / 3 = 8.5

Header Files Used

1.#include <iostream>

Provides cout and cin for input/output operations.

2.#include <iomanip>

Provides setprecision() and fixed for formatting decimal output.

Essential for displaying averages with specific decimal places.

Declaring Variables

The program declares:

float num1, num2, num3;

float is used to handle decimal numbers.

num1, num2, num3 store the three numbers entered by the user.

Taking Input From the User

The program asks:

cin >> num1 >> num2 >> num3;

The user enters three numbers, for example: 10 20 30

The >> operator can chain multiple inputs, reading them sequentially.

1cout << "Enter three numbers: ";

Calculating the Average

The calculation is done using:

float average = (num1 + num2 + num3) / 3.0;

How it works

First, sum all three numbers: num1 + num2 + num3

Then, divide by 3.0 (using 3.0 ensures floating-point division)

Store the result in the variable average

Why 3.0 instead of 3?

Using 3.0 ensures floating-point division.

If you use 3 (integer), the division might truncate to integer.

Example: (10 + 20 + 30) / 3.0 = 20.0 (correct)

Example: (10 + 20 + 30) / 3 = 20 (works here, but can lose precision)

Formatting the Output

To display the result with 2 decimal places:

fixed displays numbers in fixed decimal notation (not scientific).

setprecision(2) shows exactly 2 decimal places.

Example: 20 becomes 20.00, 20.5 becomes 20.50

1cout << fixed << setprecision(2);

Displaying the Result

The program prints:

<< " = " << average << endl;

Output:

Average of 10.00, 20.00, and 30.00 = 20.00

This clearly shows the input numbers and the calculated average.

1cout << "Average of " << num1 << ", " << num2 << ", and " << num3

Understanding the Average Formula

Mathematical Definition

Average = (Sum of all numbers) / (Count of numbers)

For three numbers:

Average = (a + b + c) / 3

Properties

The average is always between the minimum and maximum values.

If all numbers are equal, the average equals that number.

The average represents the "center" of the data.

Example Calculation

Numbers: 10, 20, 30

Sum: 10 + 20 + 30 = 60

Count: 3

Average: 60 / 3 = 20

Other Methods (Mentioned but not shown in code)

Method 2: Using Functions

float calculateAverage(float a, float b, float c) {

}

Encapsulates calculation in a function.

Makes code reusable and modular.

1return (a + b + c) / 3.0;

Method 3: Using Arrays

float numbers[3];

float sum = 0;

for (int i = 0; i < 3; i++) {

cin >> numbers[i];

sum += numbers[i];

}

float average = sum / 3.0;

Uses array to store numbers.

More flexible for handling multiple numbers.

Method 4: Using Templates

template<typename T>

T average(T a, T b, T c) {

}

Template function works with different data types.

More generic and reusable.

1return (a + b + c) / 3.0;

When to Use Each Method

Basic Formula

: Best for learning - simple and straightforward.

Functions

: Best for code organization - reusable and modular.

Arrays

: Good for handling many numbers - scalable approach.

Templates

: Best for generic code - works with different types.

Best Practice

: Use the basic formula for simple cases, or functions for better code organization.

Important Considerations

Data Type Selection

Use float or double for decimal numbers.

Use int only if you're certain all inputs are integers.

float is sufficient for most cases, double for higher precision.

Division by Zero

This program divides by 3, which is never zero.

For variable count, check if count > 0 before dividing.

Precision

Floating-point arithmetic may have precision limitations.

For exact calculations, consider using appropriate precision.

Common Use Cases

Statistics

Calculating mean values.

Data analysis and reporting.

Statistical computations.

Programming Practice

Basic arithmetic operations.

Understanding floating-point division.

Input/output formatting.

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