$\displaystyle\pi\usepackage{cmbright}\Huge\$ is a non-terminating, non-repeating decimal, so it is an irrational number. Think about where $\displaystyle{2}\sqrt{{{5}}}\usepackage{cmbright}\Huge\$ and $\displaystyle-\sqrt{{{12}}}\usepackage{cmbright}\Huge\$ could be placed on the number line; is either of these a terminating or repeating decimal?