Answer
$=\dfrac {2}{3}$
Work Step by Step
$0.\overline {6}=0.666...=\dfrac {6}{10}+\dfrac {6}{10^{2}}+\dfrac {6}{10^{3}}...=\dfrac {a_{1}}{1-r}=\dfrac {\dfrac {6}{10}}{1-\dfrac {1}{10}}=\dfrac {\dfrac {6}{10}}{\dfrac {9}{10}}=\dfrac {6}{9}=\dfrac {2}{3}$