Rationalizing Demoninators

$\frac{\sqrt{72}}{\sqrt{10}} = \frac{\sqrt{2} \sqrt{36}}{\sqrt{2} \sqrt{5}} = \frac{6}{\sqrt{5}}$

$\frac{6}{\sqrt{5}} \cdot \frac{\sqrt{5}}{\sqrt{5}} = \boxed{\frac{6\sqrt{5}}{5}}$