C Program to find Sum of Geometric Progression Series

Write a C Program to find the Sum of the Geometric Progression Series (G.P. Series) using a Math Formula, and without using a Mathematical formula.

Geometric Progression Series

A geometric Series is a sequence of terms in which the next element is obtained by multiplying the common ratio by the previous element. Or G.P. Series is a series of numbers in which a common ratio of any consecutive numbers (items) is always the same.

The mathematical formula behind this Sum of G.P Series
Sn = a(rⁿ) / (1- r)
Tn = ar^(n-1)

C Program to find Sum of Geometric Progression Series Example

It allows the user to enter the first value, the total number of items in a series, and the common ratio. Next, it will find the sum of the Geometric Progression Series. Here, we used For Loop to display the G.P series, which is optional. Refer to the For Loop in C.

/* Program to find Sum of Geometric Progression Series */
#include <stdio.h>
#include<math.h>
int main() {
    
    int a, n, r;
    float tn, sum = 0;
    
    printf(" Please Enter First Number of an G.P Series:  ");
    scanf("%d", &a);
    printf(" Please Enter the Total Numbers in this G.P Series:  ");
    scanf("%d", &n);
    printf(" Please Enter the Common Ratio:  ");
    scanf("%d", &r);
    
    sum = (a * (1 - pow(r, n ))) / (1- r);
    tn = a * (pow(r, n - 1));
    
    printf("\n The Sum of Geometric Progression Series =  %.2f", sum);
    printf("\n The tn Term of Geometric Progression Series = %.2f \n", tn);
    return 0;
}

 Please Enter First Number of an G.P Series:  1
 Please Enter the Total Numbers in this G.P Series:  5
 Please Enter the Common Ratio:  2

 The Sum of Geometric Progression Series =  31.00
 The tn Term of Geometric Progression Series = 16.00

In this C Program, we are not using any Mathematical formula.

/* Program to find Sum of Geometric Progression Series */
#include <stdio.h>
#include<math.h>
int main() {
    
    int a, n, r, value, i;
    float sum = 0;
    
    printf(" Please Enter First Number of an G.P Series:  ");
    scanf("%d", &a);
    printf(" Please Enter the Total Numbers in this G.P Series:  ");
    scanf("%d", &n);
    printf(" Please Enter the Common Ratio:  ");
    scanf("%d", &r);
    
    value = a;
    printf("G.P Series  :  ");
    for(i = 0; i < n; i++)
    {
        printf("%d  ", value);
        sum = sum + value;
        value = value * r;
    }
    printf("\n The Sum of Geometric Progression Series =  %f\n", sum);
    return 0;
}

 Please Enter First Number of an G.P Series:  2
 Please Enter the Total Numbers in this G.P Series:  5
 Please Enter the Common Ratio:  2
G.P Series  :  2  4  8  16  32  
 The Sum of Geometric Progression Series =  62.000000

C Program to calculate the Sum of Geometric Progression Series using Functions

This geometric progression C Program is the same as above. However, we separated the C Programming logic using Functions in C

/* Program to find Sum of Geometric Progression Series */
#include <stdio.h>
#include<math.h>
int sumofGP(int a, int n, int r)
{
    int sum = (a * (1 - pow(r, n))) / (1- r);
    return sum;
}

int main() {
    
    int a, n, r;
    float sum = 0;
    
    printf(" Please Enter First Number of an G.P Series:  ");
    scanf("%d", &a);
    printf(" Please Enter the Total Numbers in this G.P Series:  ");
    scanf("%d", &n);
    printf(" Please Enter the Common Ratio:  ");
    scanf("%d", &r);
    
    sum = sumofGP(a, n, r);
    printf("\n The Sum of Geometric Progression Series =  %f\n", sum);
    return 0;
}

Program to find Sum of Geometric Progression Series

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