SOLUTION: if seventh term of geometric sequence is 64 and sum of first ten terms is 1023 then find the sum of fifteen terms of gs.

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Question 850701: if seventh term of geometric sequence is 64 and sum of first ten terms is 1023 then find the sum of fifteen terms of gs.
Answer by richwmiller(17219) About Me  (Show Source):
You can put this solution on YOUR website!
Tn = t1 * r^(n - 1)
64 = t * r^(6)
Sum =t1*(1 - r^n)/(1 - r)
1023 = t*(1 - r^10)/(1 - r),
64 = t * r^(6)
r=2., t=1.
S =1*(1 - 2^15)/(1 - 2)
S = 32767