Basic College Mathematics (9th Edition)

$A$ = 9 mi$^{2}$ $P$ = 12 mi
Since the length and width of the preserve are the same it is a square. Area of a square: $A$ = $s$$^{2}$ $A$ = (3 mi) $^{2}$ $A$ = 9 mi$^{2}$ Perimeter of a square: $P$ = 4$s$ $P$ = 4(3 mi) $P$ = 12 mi