SOLUTION: Find the sum of the first 8 terms of a geometric series if the first term is 10 and the common ratio is 3.

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Question 1206544: Find the sum of the first 8 terms of a geometric series if the first term is 10 and the common ratio is 3.
Answer by ikleyn(52792) About Me  (Show Source):
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Find the sum of the first 8 terms of a geometric series if the first term is 10 and the common ratio is 3.
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Use the formula for the sum of the first n terms of a GP 

    S%5Bn%5D = a%5B1%5D%2A%28%28r%5En-1%29%2F%28r-1%29%29 = 10%2A%28%283%5E8-1%29%2F%283-1%29%29 = 10%2A%286560%2F2%29 = 10*3280 = 32800.    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.