Answer:
[tex]10\sqrt{6}[/tex] feet by [tex]\frac{20}{3}\sqrt{6}[/tex] ft
Step-by-step explanation:
If the length is [tex]l[/tex], then the width is [tex]\frac{2}{3}l[/tex].
Using the formula for the area of a rectangle,
[tex]l \cdot \frac{2}{3}l=400 \\ \\ \frac{2}{3}l^2=400 \\ \\ l^2=600 \\ \\ l=10\sqrt{6}[ \\ \\ \implies w=\frac{20}{3}\sqrt{6}[/tex]