Permutation
Permutation is an arrangement in a definite order of things . Eg : Arrange 3 distinct books : Red , Blue & Green books .
In how many ways we can arrange ( 1,2,3,4 )?
There are 64 ways of arranging the numbers 1,2,3,4 . ( 64 = 4 * 3 * 2 * 1 )
It is very difficult to find the number of arrangement by actually arranging them if the number of items is more . E . g .: if we want to know how many ways we can arrange 1,2,3,4,5,6,7,8,9 . It will be difficult to tell by actually arranging it . That is when permutation come to rescue .
Permutation formula gives us easy way to find number of arrangements for a given data .