C program to Find the Sum of Geometric Progression Series

/*
 * C Program to Find the Sum of G.P Series
 */
#include <stdio.h>
#include <math.h>
 
int main()
{
    float a, r, i, last_term, sum = 0;
    int n;
 
    printf("Enter the first term of the G.P. series: ");
    scanf("%f", &a);
    printf("Enter the total numbers in the G.P. series: ");
    scanf("%d", &n);
    printf("Enter the common ratio of G.P. series: ");
    scanf("%f", &r);
    sum = (a *(1 - pow(r, n + 1))) / (1 - r);
    last_term = a * pow(r, n - 1);
    printf("last_term term of G.P.: %f", last_term);
    printf("\n Sum of the G.P.: %f", sum);
    return 0;
}

Output:

Enter the first term of the G.P. series: 3
Enter the total numbers in the G.P. series: 7
Enter the common ratio of G.P. series: 2
last_term term of G.P.: 192.000000
Sum of the G.P.: 765.000000