Answer
$\frac{4}{5}$
Work Step by Step
When we are taking the square root of something, we want to find what number, when squared, is equal to the number under the square root symbol.
$(\frac{4}{5})(\frac{4}{5})=\frac{16}{25}$
Therefore, it follows that:
$\sqrt {\frac{16}{25}}=\frac{4}{5}$
