Answer
$2.0\times10^3 \text{ pounds per cubic feet}$
Work Step by Step
Using $D=\dfrac{M}{V}$ or the density of an object, then
\begin{array}{l}\require{cancel}
D=\dfrac{M}{V}
\\
D=\dfrac{500,000}{250}
\\
D=2,000
.\end{array}
In scientific notation, the density is $
2.0\times10^3 \text{ pounds per cubic feet}
.$
