Answer
$4\text{ }g/cm^3$
Work Step by Step
Using $D=\dfrac{m}{V}$ or the formula for the density of an object, with $m=\sqrt{80}$ and $V=\sqrt{5},$ then
\begin{align*}\require{cancel}
D&=\dfrac{\sqrt{80}}{\sqrt{5}}
\\\\&=
\sqrt{\dfrac{80}{5}}
&\left(\text{use }\dfrac{\sqrt[n]{x}}{\sqrt[n]{y}}=\sqrt[n]{\dfrac{x}{y}} \right)
\\\\&=
\sqrt{16}
\\&=
4
.\end{align*}
Hence, the density, $D,$ of the object is $
4\text{ }g/cm^3
$.
