Insert a rational and an irrational number between 2 and 2.5.

As, few rational numbers between 2 and 2.5 are: 2.1, 2.2, 2.3, 2.4, ...

And,

Since, $2=\sqrt{4}$ and $2.5=\sqrt{6.25}$

So, irrational number between 2 ans $2.5$ are: $\sqrt{4.1}, \sqrt{4.2}, \ldots, \sqrt{5}, \ldots$

Hence, a rational and an irrational number can be $2.1$ and $\sqrt{5}$, respectively.

Disclaimer: There are infinite rational and irrational numbers between any two rational numbers.