The ancient Greek mathematician Euclid proved in his Elements of Geometry that there are only five Platonic solids – the regular tetrahedron (four sides that are equilateral triangles), the cube (six ...

So only three Platonic solids can be made from triangles. Image caption, Three squares make the corner of a cube. However four squares just make a flat sheet that can’t be folded into a corner.

There are five platonic solids, the tetrahedron, cube, octahedron, dodecahedron and icosahedron. A prism is a 3D shape with a constant polygon shaped cross-section. A prism is named by the shape ...