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.