Question 1093042
As the perimeter (the length of the fence) changes by a certain factor,
while the shape stays the same,
the surface area changes by the square of the factor.
{{{drawing(150,150,-1.1,1.1,-1.1,1.1,
rectangle(-1,-1,1,1) )}}} --> {{{drawing(300,300,-2.2,2.2,-2.2,2.2,
red(rectangle(-2.03,-2.03,2.03,2.03)),
rectangle(0,0,-2,-2),rectangle(0,0,2,-2),
rectangle(0,0,-2,2),rectangle(0,0,2,2) )}}} {{{drawing(100,100,-1.1,1.1,-1.1,1.1,
rectangle(-1,-1,1,1) )}}} --> {{{drawing(300,300,-3.3,3.3,-3.3,3.3,
rectangle(-3,-3,3,3),rectangle(-1,-1,1,1),
rectangle(-1,1,-3,3),rectangle(1,1,3,3),
rectangle(-3,-3,-1,-1),rectangle(1,-1,3,-3) )}}} 
So, doubling the perimeter, quadruples the surface area.
{{{(160acres)*(4miles/"2 miles")^2=(160acres)*2^2=(160acres)*4=highlight(640acres)}}}