A rational number can be written as $\frac{a}{b}$, where $a,b\in \mathbb{Z}$ and $b\ne 0$. An irrational number has a decimal expansion that continues forever without recurring.

$6\sqrt{2}$

For $a,b\ge 0$, $\sqrt{ab}=\sqrt{a}\sqrt{b}$. For $a\ge 0$ and $b>0$, $\boxed{\sqrt{\frac{a}{b}}=\frac{\sqrt{a}}{\sqrt{b}}}$.

Converting to decimals introduces rounding errors.