Question

What is the sum of a 6–term geometric series if the first term is 6 and the last term is 1,000,842?

Answer 1

a. 138,073
b. 117,648
c. 188,851
d. 157,962

Answer 2

First you have to do:
\[a_{6} = a_{1}r^{6 - 1}\]\[1000842 = 6r^{5}\]Can you solve for r now?

Answer 3

What do I do with the 5?

Answer 4

Well, did you first divide by 6?

Answer 5

Yes.

Answer 6

\[r = \sqrt[5]{166807}\]

Answer 7

After you get r, then plug it into this formula.
\[S_{n} = \frac{a_{1}(1 - r^{n})}{1 - r}\]\[S_{6} = \frac{6(1 - r^{6})}{1 - r}\]

Answer 8

Note: You need a scientific caluculator or use a web calculator.