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Which of the following statements are TRUE?

Select ALL that apply.

$\sqrt [3] {27} \leq \sqrt [4] {81}$

$\sqrt {100} > 10$

$\sqrt \frac { 1 }{ 4 }=\cfrac {\sqrt 1} {\sqrt [3] 8}$

$\sqrt 13 \cdot \sqrt [3] {3}=\sqrt { 39 }$

$(-3)^3=3^3$

$\sqrt 5 + 2\sqrt 5 = 3\sqrt 5 $