The area of a rectangle is given by:
[tex]A=w\cdot l[/tex]Where "A" is the area, "w" is the width and "l" is the length.
In this problem the area of the lot is equal to "1 square mile" and the length is "1 mile". We can find the width with this information, we just need to use them in the formula above.
[tex]\begin{gathered} 1=1\cdot w \\ 1=w \\ w=1 \end{gathered}[/tex]The width is also 1 mile.
