After folding the piece of paper, the result will be 1/4 the size of the original square. If you multiply the are of the triangle by 4, you will find that the area of the original square is 36 square inches. The square root of 36 is 6, which shows us that the length of each side of the square is 6. To get the perimeter, multiply 6 by 4 to get 24 inches.
The answer is HL. HL is a theorem stating that if the hypotenuse and one leg are congruent to another pair of hypotenuse and leg then the triangles themselves are congruent. Hope this helps.
