C#: Display the sum of the series [ 9 + 99 + 999 + 9999 ...]

C# Sharp For Loop: Exercise-21 with Solution

Write a program in C# Sharp to display the sum of the series [ 9 + 99 + 999 + 9999 ...].

Sample Solution:-

C# Sharp Code:

using System;  // Importing necessary namespace

public class Exercise21  // Declaration of the Exercise21 class
{  
    public static void Main()  // Main method, entry point of the program
    {   
        int n, i, t = 9;  // Declaration of variables n, i, t with initialization
        int sum = 0;  // Variable to store the sum, initialized to 0

        Console.Write("\n\n");  // Displaying new lines
        Console.Write("Display the sum of the series [ 9 + 99 + 999 + 9999 ...]:\n");  // Displaying the purpose of the program
        Console.Write("-----------------------------------------------------------");  // Displaying a separator
        Console.Write("\n\n");

        Console.Write("Input the number or terms :");  // Prompting the user to input the number of terms
        n = Convert.ToInt32(Console.ReadLine());  // Reading the number of terms entered by the user

        // Loop to generate the series and calculate the sum
        for (i = 1; i <= n; i++)
        { 
            sum += t;  // Adding the current value of t to the sum
            Console.Write("{0}   ", t);  // Displaying the current value of t
            t = t * 10 + 9;  // Generating the next value of t for the series
        }

        Console.Write("\nThe sum of the series = {0} \n", sum);  // Displaying the sum of the series
    }	
}

Sample Output:

                                  
Display the sum of the series [ 9 + 99 + 999 + 9999 ...]:                                                                                                      
-----------------------------------------------------------                            
Input the number or terms :5                                                                                                         
9   99   999   9999   99999                                                                                                         
The sum of the saries = 111105

Flowchart:

C# Sharp Code Editor:

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