Answer:
80 feet by 20 feet
Step-by-step explanation:
Area of the rectangular enclosure = 1600ft²
Area, lw=1600
w=1600/l
Perimeter, 2w+l=120 feet
Substituting w=1600/l into the perimeter
2(1600/l)+l=120
3200/l+l=120
[tex]\dfrac{3200+l^2}{l}=120\\ 3200+l^2=120l\\l^2-120l+3200=0\\l^2-40l-80l+3200=0\\l(l-40)-80(l-40)=0\\(l-40)(l-80)=0\\l-40=0\:or\:l-80=0\\l=40\:or\:l=80[/tex]
When l=40, w=1600/40=40 feet
When l=80, w=1600/80=20 feet
Since the enclosure is rectangular, the acceptable dimensions are:
Length =80 feet
Width =20 feet