A permutation is an arrangement of objects in a specified order. The

total number of ways to arrange 'r' items out of total 'n' items,

regarding the order of selection, is

In the given question

total number of ways to arrange 'r' items out of total 'n' items,

regarding the order of selection, is

^{n}P_{r}.^{n}P_{r}= n!/(n-r)!In the given question

^{4}P_{3}, n=4 and r=3.^{4}P_{3}= 4!/ (4-3)!^{4}P_{3}= 4!/ 1!^{4}P_{3}= 24