Given the geometric sequence: 9, 3, 1, ... . Find S6

Given the geometric sequence:   9,  3,  1,  ...  .      Find S6

ratio r =  $$\small{\text{$
\frac{3}{9}=\frac{1}{3} $}}$$ and $$\small{\text{$a=9$}}$$ so

$$\small{\text{$
\boxed{a_n=a\cdot
\left(
\frac{1}{3}\right)^{n-1}}
$}}$$

$$s_6=9+3+1+\frac{1}{3}+\frac{1}{9}+\frac{1}{27}\\ \\
s_6=13+0.\overline{481}\\\\
s_6=13.\overline{481}$$