Answer
$\frac{9}{11}$
Work Step by Step
$0.\overline {81}=0.818181\ldots =\dfrac {81}{100}+\dfrac {81}{100^2}+\dfrac {81}{100^3}\ldots =\dfrac {a_{1}}{1-r}=\dfrac {\dfrac {81}{100}}{1-\dfrac {1}{100}}=\dfrac {81}{99}=\dfrac {9}{11}$
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