Five identical triangles can be arranged to show squares on each of the triangles sides, but one at a time.
Place the blocks on either the overhead projector or the ELMO.Select the yellow triangle.Along the hypotenuse of the yellow triangle arrange a square using four red triangles in a square so that their hypotenuses are pointing out.Along the side arrange two red triangles in a square with the hypotenuses pointing inward.
5 triangles