Question

Find the area of a 2-inch-wide decorative border around a rectangular canvas painting, where L is the length and W is the width of the canvas painting. (Formula for area of a rectangle: A equals L times W)

Answer 1

4L +4W +16 square inches

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