SOLUTION: A geometric progression has a first term of a, common ratio of r and its 6th term is 768. Another geometric progression has a first term of a, common ratio of 6r and its 3rd term i

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Question 1175257: A geometric progression has a first term of a, common ratio of r and its 6th term is 768. Another geometric progression has a first term of a, common ratio of 6r and its 3rd term is 3456. Evaluate a and r.
Answer by ewatrrr(24785) About Me  (Show Source):
You can put this solution on YOUR website!

Hi
an = ar^(n -1)
a3 = a(6r)^2 = 3465 = 36ar^2  a = 3456/(36r^2)
a6= ar^(6 -1) = ar^5 = +%283456%2F36r%5E2%29%28r%5E5%29+=+768
 r^3 = 768(36/3456) = 8
  r = 2   and a = 24        3456%2F144
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