Question

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.

Answer 1

ar^3/ar^11 = 1/r^8 = 1/2^8
so, r = 2

I expect you can take it from there...

Answer 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

Answer 3

Thanks

Answer 4

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