In this tutorial, we will learn and write a program to find the sum of GP series in C++. Before that, you may go through the following topics in **C++ programming**:

The program takes the first term, the common ratio and the number of terms as input and calculates the GP on a separate function.

**C++ Program to Calculate Sum of Geometric Progression**

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 | #include <iostream> using namespace std; void gpFunc(float, float, int); int main() { int n; float a, r; cout << "Enter the first term (a): "; cin >> a; cout << "Enter the common ratio (r): "; cin >> r; cout << "Enter the no. of terms (n): "; cin >> n; //calling function gpFunc(a, r, n); } void gpFunc(float a, float r, int n) { float sum = 0, temp = a; for (int i = 1; i < n; i++) { sum = sum + temp; temp = temp * r; } cout << "\nSum of geometric progression: " << sum; } |

**Output:**

`Enter the first term (a): 1`

Enter the common ratio (r): 2

Enter the no. of terms (n): 10

Sum of geometric progression: 511