# The Sum of Some (Infinite) Series Are Finite

Like the title says!

One concrete example is **geometric series** (but only when each term is some fraction of the previous).

Here’s the formula that dictates the resultant finite sum:

- is known as your “starting” amount
- is the “multiple” (remember, in a geometric series, each term is some “multiple” of the previous term)
- must be less than 1 in order for this sum to be finite (i.e. this formula assumes r less than 1!)
- so not
*all*geometric series result in a finite sum, only ones with less than one

That’s kinda cool!