Free interactive math game: Tessellation — Which shape tiles?. Part of the Geometric Shapes category on MathKite.
Taken from the generator that powers this exercise. A fresh set appears every time the page is opened, and the printable worksheet holds ten of them.
Which shapes tile a flat surface with no gaps and no overlaps.
Look at the angles meeting at a corner. They have to add to exactly 360 degrees, because a full turn is what closes the gap around a point.
Regular hexagons tessellate because three of their 120-degree angles meet at 360 exactly.
Assuming every regular polygon tiles. A pentagon has 108-degree angles, and no whole number of those reaches 360, so gaps are unavoidable.