SOLUTION: The sum of the first 4 terms of geometric series is 15 and sum of the next four terms is 240. Determine the positive constant ratio.

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Question 1065935: The sum of the first 4 terms of geometric series is 15 and sum of the next four terms is 240. Determine the positive constant ratio.
Answer by KMST(5328) About Me  (Show Source):
You can put this solution on YOUR website!
b%5B1%5D= the first term
r= the constant ratio
The sum of the first 4 terms is
.
The sum of the next 4 terms is
.
The ratio of the two sums is
,
which simplifies to
r%5E4=16 .
So, the positive constant ratio is highlight%28r=2%29 .
No need to use the formula for sum of the first n terms.