機率一題

\(\frac{1}{6}+\frac{5}{6}\times \frac{1}{6}+{{\left( \frac{5}{6} \right)}^{2}}\times \frac{1}{6}+{{\left( \frac{5}{6} \right)}^{3}}\times \frac{1}{6}+\cdots +{{\left( \frac{5}{6} \right)}^{n-1}}\times \frac{1}{6}>0.9\)