Explanation:

- Consider the third number as $x$.

- The first number is 20% more than $x$, which is $1.2x$.

- The second number is 10% more than $x$, which is $1.1x$.

- Calculate the ratio of the first number to the second number:

$$

\frac{1.2x}{1.1x} = \frac{1.2}{1.1} = \frac{12}{11}

$$

- The ratio simplifies to 12:11.

- Option 4: 12 : 11 is the correct answer.