C++ Exercises: Find the Sum of GP series

Last update on August 14 2025 12:55:16 (UTC/GMT +8 hours)

32. Sum of a G.P. Series

Write a C++ program to find the sum of the GP series.

Visual Presentation:

C++ Exercises: Find the Sum of GP series

Sample Solution:-

C++ Code :

#include <iostream> // Include the input/output stream library
#include <math.h>   // Include the math library for mathematical functions
using namespace std; // Using standard namespace

int main() // Main function where the execution of the program starts
{
    float g1, cr, i, n, j; // Declare float variables g1, cr, i, n, j
    int ntrm, gpn; // Declare integer variables ntrm and gpn
    float sum = 0; // Declare and initialize a float variable sum to 0

    // Display message asking for input
    cout << "\n\n Find the Sum of GP series:\n";
    cout << "-------------------------------\n";
    cout << " Input  the starting number of the G.P. series: ";
    cin >> g1; // Read input for the starting number of the G.P. series

    cout << " Input the number of items for  the G.P. series: ";
    cin >> ntrm; // Read input for the number of items for the G.P. series

    cout << " Input the common ratio of G.P. series: ";
    cin >> cr; // Read input for the common ratio of the G.P. series

    /*-------- generate G.P. series ---------------*/
    cout << "\nThe numbers for the G.P. series:\n ";
    cout << g1 << "  "; // Display the starting number of the G.P. series
    sum = g1; // Set sum to the starting number

    // Loop to generate and display the G.P. series terms
    for (j = 1; j < ntrm; j++) {
        gpn = g1 * pow(cr, j); // Calculate each term of the G.P. series
        sum = sum + gpn; // Add the term to the sum
        cout << gpn << "  "; // Display the generated term
    }
    /*-------- End of G.P. series generate ---------------*/

    cout << "\n The Sum of the G.P. series:  " << sum << endl; // Display the sum of the G.P. series
}

Sample Output:

 Find the Sum of GP series:                                            
-------------------------------                                        
 Input  the starting number of the G.P. series: 3                      
 Input the number of items for  the G.P. series: 5                     
 Input the common ratio of G.P. series: 2                              
                                                                       
The numbers for the G.P. series:                                       
 3  6  12  24  48                                                      
 The Sum of the G.P. series:  93

Flowchart:

For more Practice: Solve these Related Problems:

Write a C++ program to compute the sum of a geometric progression given its first term, common ratio, and number of terms.
Write a C++ program that reads the first term, ratio, and n, then outputs the G.P. series and its total sum.
Write a C++ program to generate a G.P. series and calculate the sum using a loop and the formula for geometric sums.
Write a C++ program that compares the iterative summation of a G.P. series with its formula-based calculation.

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