Because the paper is folded diagonally, you already know the two straight side lengths but not the diagonal. The triangle is a right triangle so you van use the Pythagorean Theorem to find the diagonal. The Pythagorean Theorem = a^2+b^2=c^2 so 8.5^2+8.5^2=144.5^2 144.5^2=12.02 The diagonal of the right triangle would then be 12.02 inches. Hope this helps!!
