How do you find the sum of the geometric series $3+1+1/3+...$ to 7 terms?

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Answer 1 · 2017-07-08T13:48:32

$4.50$ (3sf)

Use the formula for sum of a geometric series:

$S=(a(1-r^n))/(1-r)$

where $-1 < r < 1$

$a$ is the first term, $r$ is the common ratio and $n$ is the number of terms required.

$S=(3(1-(1/3)^7))/(1-1/3)$

Put this into your calculator and I think it gives the answer above.

How do you find the sum of the geometric series 3+1+1/3+...3+1+1/3+... to 7 terms?