g.p.

The ratio of the fourth and 12th term of a g.p. With positive common ratio is 1:256. If the difference of two terms be 61.2, find the sum of 8 terms of this series.

asked by warnar
  1. ar^3/ar^11 = 1/r^8 = 1/2^8
    so, r = 2

    I expect you can take it from there...

    posted by Steve
  2. This might help you to learn about a.p. and g.p.:

    http://www.mathcentre.ac.uk/resources/uploaded/mc-ty-apgp-2009-1.pdf

    posted by MathMate
  3. Thanks

    posted by Warnar
  4. I don't trust anyone who tries to impersonate me and can't even get my name right.

    posted by Ms. Sue

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