Happy Wednesday math friends! In today’s post we are going to go over what finding the sum of a finite geometric series means and then use the **finite geometric series formula **to solve an example step by step. If you need a refresher on geometric sequences before tackling these types of questions, don’t hesitate to check out this post here. Maybe you’re looking for infinite geometric series, check out the previous link? Also, don’t forget to check out the video that explains everything you see here as well as practice questions below. Happy calculating! 🙂

**What does it mean to find the “Sum of the Finite Geometric Sequence”?**

We already know what a **geometric sequence** is: a sequence of numbers that form a pattern when the same number is *multiplied* or *divided* to each term.

Example:

But when what happens if we wanted to **sum the terms of our geometric sequence** together?

Example:

More specifically, what if we wanted to find the **sum of the first 20 terms** of the above Geometric Sequence? How would we calculate that? That’s where our **Finite Geometric Series Formula **will come in handy!

**Finite Geometric Series Formula:**

Now that we have a formula to work with, let’s take another look at our question and apply our finite geometric series formula to answer the solution:

## Finite Geometric Series Example:

**Step 1: **First let’s write out our formula and identify what each part represents/what numbers need to be fill in.

**Step 2: **Now let’s fill in our formula and solve with the given values.

Try the similar practice questions below!

## Practice Questions:

1) Find the sum of the first 15 terms of the following geometric sequence:

4, 12, 36, 108, ….

2) Find the sum of the first 12 terms of the following sequence and round to the nearest tenth:

128, 64, 32, 16, ….

3) Find the sum of the first 18 terms of the following geometric sequence and round to the nearest tenth:

400, 100, 25, 6.25, ….

4) Find the sum of the first 12 terms of the following geometric sequence:

3, 6, 12, 24, ….

**Solutions:**

1) 28,697,812

2) 255.9

3) 533.3

4) 12,285

Still got questions? No problem! Don’t hesitate to comment with any questions below. Thanks for stopping by and happy calculating! 🙂

Facebook ~ Twitter ~ TikTok ~ Youtube

Check out similar posts for Algebra 2/Trig. here! And if you want to learn about even more sequences, check out the link here!

Related Posts:

## 3 thoughts on “Finite Geometric Series Formula: Algebra 2”