Centre of Gravity Lines and Centre of a Tetrahedron
Here above is a Giant Tetrahedron built with:
-168 purple Geofix Small Equilateral Triangles
-16 blue Geofix hexagons and
-36 orange Geofix Squares

To demonstrate its centre of gravity we used:
-4 x 4 yellow Connectors Nr.2
-1 x 4 clear Connectors Nr.1
-9 x 4 orange Connectors Nr.2
-4 x 4 yellow Minigeofix Squares
-4 red Minigeofix Hexagons
-4 red Minigeofix Triangles		 An alternative way of highlighting the centre of gravity lines and centre of a Tetrahedron is shown below. For this model we used only Minigeofix shapes:

-268 Minitriangles (red & yellow)
-132 yellow Minisquares &
-20 red Minihexagons