How do you find $a_2$ for the geometric series given $S_n=315$ , r=0.5, n=6?

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Answer 1 · 2016-11-11T20:24:23

$s_n = (a(1 -r^n))/(1 - r)$

$315 = (a(1 - 0.5^6))/(1- 0.5)$

$315(0.5) = (a(1- 0.015625))$

$157.5 = 0.984375a$

$a = 160$

Now, use the formula $t_n = a xx r^(n - 1)$ to find the 2nd term.

$t_2 = 160 xx 0.5^(2- 1)$

$t_2 = 160 xx 0.5$

$t_2 = 80$

Hopefully this helps!

How do you find a_2a_2 for the geometric series given S_n=315S_n=315, r=0.5, n=6?