Answer
$\dfrac{11}{3\sqrt[]{11}}$
Work Step by Step
Multiplying both the numerator and the denominator by a factor that will make the numerator a perfect power of the radical, the rationalized-numerator form of the given expression, $
\dfrac{\sqrt[]{11}}{3}
,$ is
\begin{array}{l}\require{cancel}
\dfrac{\sqrt[]{11}}{3}\cdot\dfrac{\sqrt[]{11}}{\sqrt[]{11}}
\\\\=
\dfrac{\sqrt[]{(11)^2}}{3\sqrt[]{11}}
\\\\=
\dfrac{11}{3\sqrt[]{11}}
.\end{array}