Question

Calculati : $( \frac{3}{ \sqrt{18} } + \frac{8}{ \sqrt{32} } + \frac{6}{ \sqrt{72} } ) : ( \frac{5}{2 \sqrt{2} } )^{-1}$ .

Answer 1

$...=\left(\dfrac{3}{3\sqrt2}+\dfrac{8}{4\sqrt2}+\dfrac{6}{6\sqrt2}\right)\cdot\dfrac{5}{2\sqrt2}=\ (dupa \ simplificari)\ =$

$=\dfrac{4}{\sqrt2}\cdot\dfrac{5}{2\sqrt2}=\dfrac{20}{4}=5$