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December 20, 2014

December 20, 2014

Posted by **Bob** on Monday, June 3, 2013 at 9:58pm.

in a geometric series t1=23,t3=92 and the sum of all of the terms of the series is 62813. How many terms are in the series?

- math -
**Reiny**, Monday, June 3, 2013 at 10:20pmt1 = 23 ---> a = 23

t3 = 92 --->ar^2 = 92

divide them

r^2 = 4

r = ± 2

sum(n) = a(r^n - 1)/(r-1) = 62813

If r = 2

23( 2^n - 1)/(2-1) = 62813

2^n - 1 = 2731

2^n = 2732

but ....

n has to be a whole number, since it stands for the number of terms

2732 is NOT a power of 2,

so even though you typed it again with a correction , the question is still flawed.

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