well, the area of a trapezoid is A = ([tex] b_{1} [/tex] + [tex] b_{2} [/tex]) * h * 1/2 so you can use the area of a parallelogram, which is A = l * w, by splitting the trapezoid into 2 triangles and one rectangle. So you'd use A = l * w for the rectangle and A = 1/2bh for the triangles. You'd get the same answer!