Simplify Ratio 3C536E

1. **State the problem:** Simplify the ratio $9 : 81$. 2. **Formula and rules:** To simplify a ratio, divide both terms by their greatest common divisor (GCD). 3. **Find the GCD:** The GCD of $9$ and $81$ is $9$. 4. **Divide both terms by the GCD:** $$\frac{9}{\cancel{9}} : \frac{81}{\cancel{9}} = 1 : 9$$ 5. **Final answer:** The simplified ratio is $1 : 9$.