Geometric Series
Main Concept

A series is the sum of terms in a sequence. There are two types of series: finite and infinite. Finite series have defined first and last terms, and infinite series continue indefinitely.
A finite series can be written as follows:
, where for every
An infinite series can be written as follows:
, where for every
A geometric series is a series in which the term can be obtained from the previous term by multiplying by a fixed number. For instance, is a geometric series in which each successive term is found by multiplying the previous term by .
Sometimes the terms of an infinite series can be added up to give a finite number, called the sum of the series.



Consider the geometric series . Does this series have a sum?

Answer


The sum of the series is 1.
To see this, imagine that we paint a blank canvas in steps. At each step, we paint half of the unpainted area. The total area painted after steps is therefore the th partial sum,
. The total area remaining unpainted is . After an infinite number of steps we will have painted all of the canvas, of which the area is 1.
Click on the canvas to paint one section, or click "Paint All".







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