\[S_n = a_1 * (1 - r^n) / (1 - r)\]
Variables
Snsum of terms
a1first term
rcommon ratio
nnumber of terms
Description
What is this formula?
This formula computes the sum of a geometric progression.
When to use it
When dealing with exponential growth or decay series.
Example
a1=2, r=3, n=3 → Sn=2*(1-27)/(1-3)=26
Applications
Finance, physics, computer science.