What is the sum of a geometric series?

In math, the term "sum of a geometric series" describes the value when all of the terms in a geometric series are added together. The sum of the terms in a geometric series can be found using the generic formula a * ([1 - r^n]/[1 - r]).

In the generic formula, the variable a is the value of the first term, r is the common ratio that relates all of the terms in the sequence and n is the number of terms in the entire sequence. The equation to find a sum of a geometric series is expressed using the Greek sign sigma, with a value above and below it indicating the number of terms in the series.