12 Identical Blue Triangles

12 Identical Blue Triangles belong to the constructive triangles family and are alike in shape and colour, so nothing but position tells one from another. Joined edge to edge they turn into a rhombus, a trapezium and a hexagon, and the child sees the first physical proof that figures are built out of other figures. The work leads straight into later lessons on equivalence and area. For children from 3 to 6 who already know the basic plane shapes.