Answer
$150 \text{ sq. ft}$
Work Step by Step
Using $P=2l+2w$ (or the Perimeter of a Rectangle), then the perimeter of the given rectangle is
\begin{array}{l}\require{cancel}
P=2(3\sqrt{20})+2(\sqrt{125})
\\\\
P=6\sqrt{20}+2\sqrt{125}
\\\\
P=6\sqrt{4\cdot5}+2\sqrt{25\cdot5}
\\\\
P=6\sqrt{(2)^2\cdot5}+2\sqrt{(5)^2\cdot5}
\\\\
P=6(2)\sqrt{5}+2(5)\sqrt{5}
\\\\
P=12\sqrt{5}+10\sqrt{5}
.\end{array}
Hence, the perimeter is $
\left( 12\sqrt{5}+10\sqrt{5} \right) \text{ ft}
.$
Using $A=lw$ (or the Area of a Rectangle), then the area of the given rectangle is
\begin{array}{l}\require{cancel}
A=(3\sqrt{20})(\sqrt{125})
\\\\
A=3\sqrt{20(125)}
\\\\
A=3\sqrt{2500}
\\\\
A=3\sqrt{(50)^2}
\\\\
A=3(50)
\\\\
A=150
.\end{array}
Hence, the area is $
150 \text{ sq. ft}
.$
