How do you simplify 8/sqrt 10?

$\frac{8}{\sqrt{10}} = \frac{4 \sqrt{10}}{5}$

Explanation:

$\frac{8}{\sqrt{10}} = \frac{8}{\sqrt{10}} \cdot \frac{\sqrt{10}}{\sqrt{10}} = \frac{8 \sqrt{10}}{10}$

continue

$\frac{8 \sqrt{10}}{10} = \frac{2 \cdot 4 \cdot \sqrt{10}}{2 \cdot 5} = \frac{\cancel{2} \cdot 4 \cdot \sqrt{10}}{\cancel{2} \cdot 5}$

so that

$\frac{8}{\sqrt{10}} = \frac{4 \sqrt{10}}{5}$ the simplest