# How To Find Sum Of A Geometric Series

Have you ever encountered a sequence of numbers in which each term is multiplied by a constant ratio to obtain the next term? If so, you have encountered a geometric series. These series are fascinating and knowing how to calculate the sum of a geometric series can be a useful skill. Let’s delve into the intricacies of determining the sum of a geometric series.

## What is a Geometric Series?

Before we delve into finding the sum of a geometric series, let’s make sure we’re on the same page regarding what a geometric series actually is. In simple terms, a geometric series is a sequence of numbers in which each term is obtained by multiplying the previous term by a fixed, non-zero number called the common ratio.

For example, consider the series: 2, 4, 8, 16, 32, … In this series, each term is obtained by multiplying the previous term by 2. So, the common ratio here is 2.

## Finding the Sum of a Geometric Series

To find the sum of a geometric series, we have a handy formula at our disposal:

`S = a * (1 - r^n) / (1 - r)`

Here, `S` represents the sum of the series, `a` is the first term of the series, `r` is the common ratio, and `n` is the number of terms we want to sum.

Let’s break down the formula step by step to understand how it works. The numerator `(1 - r^n)` represents the difference between 1 and the common ratio raised to the power of the number of terms. The denominator `(1 - r)` accounts for the common ratio. So, by dividing the numerator by the denominator, we obtain the sum of the geometric series.

Let’s apply this formula to the series we mentioned earlier: 2, 4, 8, 16, 32, …

### Step 1:

First, we need to determine the values of `a`, `r`, and `n`. In our example, the first term `a` is 2, the common ratio `r` is 2, and let’s say we want to find the sum of the first 5 terms, so `n` is 5.

### Step 2:

Now, we can plug these values into the formula:

`S = 2 * (1 - 2^5) / (1 - 2)`

### Step 3:

Simplifying the equation further, we have:

`S = 2 * (1 - 32) / (1 - 2)`

`S = 2 * (-31) / (-1)`

`S = -62`

Therefore, the sum of the first 5 terms of the series 2, 4, 8, 16, 32 is -62.

## Conclusion

Understanding how to find the sum of a geometric series is an essential skill in the realm of mathematics. By applying the formula `S = a * (1 - r^n) / (1 - r)`, we can accurately calculate the sum of a geometric series. So the next time you encounter a series with a common ratio, don’t fear, but rather embrace the opportunity to find its sum.

Happy calculating!