Question

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

Answer 1

`4.50` (3sf)

Explanation:

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.