Question

The number of all one-one function from set{a,b,c,d} to itself is 

(a) 12

(b) 24

(c) 36

(d) none of these

Answer 1

Given set is A = {a, b, c, d}.

Total number of one - one functions

= 4 x 3 x 2 x 1 = 4! = 24.

Alternative method :-

Total number of element in set A is n = 4.

∴ Total number of one - one function from set A to itself = n! = 4! = 24.

Answer 2

Answer is (b) 24