Asquare piece of paper is folded in half vertically. the resulting figure has a perimeter of 21 inches. what is the number of square inches in the area of the original square?

check the picture below.

now we start off with a square, namely a rectangle with all equal sides, so if we cut it in half, like in the picture, and each half-side is x long, then the longer sides are 2x long, as you see there, and we know the perimeter is 21.

so since we know each side is 7 units, then the area is just 7², or 49.