To find an irrational number between 9 and 11, we can consider the square roots of certain numbers.
- \(\sqrt{100} = 10\) (which is rational and not between 9 and 11).
- \(\sqrt{20}\) is approximately 4.47 (which is less than 9).
- \(\sqrt{10}\) is approximately 3.16 (which is less than 9).
- \(\sqrt{99}\) is approximately 9.95 (which is between 9 and 11 and is irrational).
Therefore, the correct answer would be:
\(\sqrt{99}\)
This is an example of an irrational number between 9 and 11.