A row of six identical triangles. Lines divide the triangles into 3 groups of 2 triangles each. 
A row of six identical triangles. Lines divide the triangles into 3 groups of 2 triangles each.
\dfrac13 
3
1
 start fraction, 1, divided by, 3, end fraction of 6=6=6, equals 
\dfrac23 
3
2
 start fraction, 2, divided by, 3, end fraction of 6=6=6, equals