SOLUTION: Determine the sixth partial sum, P6 , of the geometric sequence: 5, (5/4), (5/16), ...

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Question 1137603: Determine the sixth partial sum, P6 , of the geometric sequence:
5, (5/4), (5/16), ...
Answer by Boreal(15235) About Me  (Show Source):
You can put this solution on YOUR website!
sum= a1(1-r^n)/(1-r)
r is 1/4
a1 is 5
sum6=5(1-.25^6)/.75
=5*1.1865=6.665
check
5+5/4+5/16+5/64+5/256+5/1024
=5+(1280+320+80+20+5)/1024
=5+(1700/1024)=6+(676/1024)=6 169/256 BEST ANSWER
=6.660, rounding the fraction