﻿ C++ : Find the sum of the series 1+11+111+1111+ .. n terms

# C++ Exercises: Find the sum of the series 1 +11 + 111 + 1111 + .. n terms

## C++ For Loop: Exercise-26 with Solution

Write a program in C++ to find the sum of the series 1 +11 + 111 + 1111 + .. n terms.

Visual Presentation:

Sample Solution:-

C++ Code :

``````#include <iostream> // Including input-output stream header

using namespace std; // Using standard namespace to avoid writing std::

int main() // Start of the main function
{
int n, i, sum = 0; // Declaration of integer variables 'n' (number of terms), 'i' (loop counter), 'sum' (to store the sum)
int t = 1; // Initializing variable 't' to 1

cout << "\n\n Display the sum of the series 1 + 11 + 111 + 1111 + .. n terms:\n"; // Displaying a message on the console
cout << "-------------------------------------------------------------------\n";
cout << " Input number of terms: "; // Prompting the user to input the number of terms
cin >> n; // Reading the input value as the number of terms

for (i = 1; i <= n; i++) // Loop to generate the series and calculate the sum
{
cout << t << " "; // Displaying the current term of the series
if (i < n) // Checking if it's not the last term to print '+'
{
cout << "+ "; // Displaying '+' to separate terms if it's not the last term
}
sum = sum + t; // Adding the current term to the sum
t = (t * 10) + 1; // Generating the next term of the series by appending '1' to the current term
}

cout << "\n The sum of the series is: " << sum << endl; // Displaying the final sum of the series
}
``````

Sample Output:

``` Display the sum of the series 1 +11 + 111 + 1111 + .. n terms:
-------------------------------------------------------------------
Input number of terms: 5
1 + 11 + 111 + 1111 + 11111
The sum of the series is: 12345
```

Flowchart:

C++ Code Editor: