Abstract
In this short paper a practical and simple proof of the Pythagorean theorem is proposed. It uses colourful interlocking plastic bricks with two shapes: a cube that measures two centimeters on each side and a right prism where the base is a right-angled isosceles triangle and the two equal rectangular faces are the same as those of the cubic brick. The proof is designed for primary school children (but also for preschool children) and begins by telling the legend of Pythagoras, who discovered his theorem by looking at the floor tile pattern of Polycrates’ palace. This proof takes into account only right-angled isosceles triangle but it is possible to show the validity of Pythagorean theorem for all right-angled triangles by building a simple proof by rearrangement.