## Lilmike234 one year ago What is the sum of the first five terms of a geometric series with a1=10 and r=1/5?

1. dumbcow

here is formula for sum of geometric series $S = \frac{a_1 (1- r^n)}{1-r}$

2. dumbcow

substituting... $S = \frac{10(1-(1/5)^5}{1- (1/5)}$

3. lilmike234

So my answer would be 12.5?