A rearrangement
of a number of objects is called a permutation.
Suppose Ann, Bob
and Carole are to sit on three chairs side by side. Then there are
6 different orders in which they could be placed on the chairs,
each being a permutation of the 3 people.
ABC BCA CAB BAC CBA ACB.
There are two main notations for such permutations. In relation
notation, one can just arrange the natural ordering of the
elements being permuted on a row, and the new ordering on
another row.
The general case is given by the formula :
where, n is the number of elements available for selection, and
r is the number of elements to be selected.
