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The sum of the first n terms in the infinite geometric sequence 1/4, 1/8, 1/16, ... is 15/32. Find n.

 Jul 3, 2021
 #1
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a1 = 1/4

r = 1/2

 

Sn = a1(1-r^n) / ( 1-r)

15/32 = 1/4(1- 1/2^n) /(1/2)

15/16 = 1-1/2 ^n

1/16 = 1/2 ^n

n= 4

 Jul 3, 2021

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