SOLUTION: Find the sum of the 1st 8 terms of the geometric series whose 1st term is 5 and whose common ratio is 3.

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Question 1207230: Find the sum of the 1st 8 terms of the geometric series whose 1st term is 5 and whose common ratio is 3.
Answer by ikleyn(52797) About Me  (Show Source):
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Apply the standard formula for the sum of the first n terms of a geometric progression

    S%5Bn%5D = a%2A%28%28r%5En-1%29%2F%28r-1%29%29,


where "a" is the first term, and "r" is the common ratio

    S%5B8%5D = 5%2A%28%283%5E8-1%29%2F%283-1%29%29 = 16400.    ANSWER

Solved.

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On geometric progressions,  see introductory lessons
    - Geometric progressions
    - The proofs of the formulas for geometric progressions
    - Problems on geometric progressions
    - Word problems on geometric progressions
in this site.