Answer:
4L +4W +16 square inches
Step-by-step explanation:
The area of the border is the equivalent of that of a rectangle with a width equal to the width of the border, and a length equal to the length of the midline of the border. That length is the perimeter of the rectangle that is L+2 units long and W+2 units wide.
border midline length = 2((L+2) +(W+2)) = 2L +2W +8
Then the border area is ...
border area = (border width)(border length) = (2)(2L +2W +8)
border area = 4L +4W +16 . . . square inches
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You can also figure this as the difference between the area of the rectangle with the border and the area of the rectangle inside the border:
border area = total area - canvas area
= (L+4)(W+4) -LW = LW +4L +4W +16 -LW
= 4L +4W +16 . . . . square inches
