# Projective Geometry/Classic/Projective Transformations/Transformations of projective 3-space/Permutation

< Projective Geometry | Classic/Projective Transformations | Transformations of projective 3-space

Many counting problem can be solved by permutation.

**permutation**-

A permutation of a set distinct objects in an ordered arrangement of these object.

**combination** is also for counting unordered selection of object.