What is an irrational number between nine and 11?

An irrational number between 9 and 11 could be √10.

To find an irrational number between 9 and 11, we can use the fact that the square root of any non-perfect square is an irrational number.

Let's calculate the square root of 10, which falls between 9 and 11:

√10 ≈ 3.16

Therefore, 3.16 is an irrational number between 9 and 11.