SOLUTION: The sum of a geometric series with seven terms is 56,133, and the common ratio is r = 3. Find the first term.

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Question 1180291: The sum of a geometric series with seven terms is 56,133, and the common ratio is r = 3. Find the first term.
Found 2 solutions by ikleyn, greenestamps:
Answer by ikleyn(52787) About Me  (Show Source):
You can put this solution on YOUR website!
.
The sum of a geometric series with seven terms is 56,133, and the common ratio is r = 3.
Find the first term.
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The formula for the sum of the GP is


    S%5Bn%5D = a%2A%28%28r%5En-1%29%2F%28r-1%29%29,


where "a" is the first term, r is the common ratio.


For this case, we have


    56133 = a%2A%28%283%5E7-1%29%2F%283-1%29%29 = a*1093.


It gives the ANSWER :  a = 56133%2F1093 = 51.35682...

Solved.

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If you do not like this ugly number, look and search for your error in the post,
because my calculations are correct.



Answer by greenestamps(13200) About Me  (Show Source):
You can put this solution on YOUR website!


As shown by tutor @ikleyn, there is likely a wrong number in your post.

Generally problems about geometric sequences involve integers, or at least "nice" fractions. The sequence does not use "nice" numbers.