Let's go through the simplification of the repeating decimal \(0.09\overline{9}\) step by step to convert it into a rational number.
We start by letting:
\[ x = 0.099999\ldots \]
Next, we multiply both sides by \(10\) to move the decimal point one place to the right:
\[ 10x = 0.99999\ldots \]
Now we have the two equations:
- \(x = 0.099999\ldots\)
- \(10x = 0.99999\ldots\)
Note that the expression \(0.99999\ldots\) is equivalent to \(1\). Thus, we can rewrite our second equation as:
\[ 10x = 1 \]
Now, we can solve for \(x\):
\[ x = \frac{1}{10} \]
This shows that:
\[ 0.09\overline{9} = \frac{1}{10} \]
In simplest form, the rational number representation is:
\[ \boxed{\frac{1}{10}} \]