SOLUTION: What is Sn of the geometric series with a1=4, an=256, and n=4? A)84 B) 336 C) 340 D)260

Algebra ->  Sequences-and-series -> SOLUTION: What is Sn of the geometric series with a1=4, an=256, and n=4? A)84 B) 336 C) 340 D)260      Log On


   

Question 855046: What is Sn of the geometric series with a1=4, an=256, and n=4?
A)84
B) 336
C) 340
D)260
Answer by richwmiller(17219) About Me  (Show Source):
You can put this solution on YOUR website!
First we need to find the ratio
Tn = t * r^(n - 1)
256 = 4 * r^(3)
r=4
S=t*(1 - r^n)/(1 - r)
S=4*(1 - 4^4)/(1 - 4)=340
C) 340