posted by warnar .
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.
ar^3/ar^11 = 1/r^8 = 1/2^8
so, r = 2
I expect you can take it from there...
This might help you to learn about a.p. and g.p.:
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