How many terms of the series 3+6+12+24+...add to 765?

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asked by Han
  1. looks like a geometric series with

    a = 3
    r = 2

    sum(n) = a(r^n -1)/(r-1)
    765 = 3(2^n - 1)/1
    255 = 2^n -1
    256 = 2^n
    2^8 = 2^n

    n = 8

    there are 8 terms

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    posted by Reiny
  2. why didn't you use this equation: 765=3(2)^n-1

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    posted by Han
  3. wait I understand thanks for your help :D

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    posted by Han

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