185.16
259.18
185.14
259.20
3 Answers

Use the geometric series formula:
a + ar + ar^2 + … + ar^n = a(1r^{n+1})/(1r).
In this case, a=216, r=1/6, and n=8, so the sum is
216(1(1/6)^9)/(1(1/6)) = 1439671/7776 = 185.142876

Hi Allie
This is a geometric series with a = 216 and r = 1/6
So a.r^n1 = 1/7776
216 (1/6)^n1 = 1/7776
(1/6)^n1 = 1/216*7776 = (1/6)8
so n1 = 8
n=9
Sum of geometric series = a (1r^n) / (1r)
= 216 (1 – (1/6)^9) / (1 – 1/6)
= 216 (6^9 – 1) /5*6^8
= (6^9 – 1) / 5*6^5 = 259.2

185.14
Source(s): Electrical Engineer