Chapter 10 - Exponents and Radicals - 10.4 Dividing Radical Expressions - 10.4 Exercise Set - Page 654: 61

$\dfrac{5}{\sqrt{55}}$

Rationalizing the numerator, the given expression, $ \sqrt{\dfrac{5}{11}} ,$ is equivalent to \begin{array}{l} \sqrt{\dfrac{5}{11}\cdot\dfrac{5}{5}} \\\\= \sqrt{\dfrac{(5)^2}{55}} \\\\= \dfrac{\sqrt{(5)^2}}{\sqrt{55}} \\\\= \dfrac{5}{\sqrt{55}} .\end{array}