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

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

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