Algebra
Intermediate

Finite Geometric Series

Sum of the first n terms of a geometric series.

Formula

Sn=a1−rn1−rS_n = a\frac{1-r^n}{1-r}

Variables

aFirst term
rRatio
nTerms

Example

2+4+8+16 = 30

Did You Know?

The geometric series formula underlies every loan and mortgage calculation ever made.

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