Given digits are 1,2,3,4.
Possibilities for units place digit (either 1 or 3) = 2
Possibilities for ten’s digit = 3
Possibilities for hundred’s place digit = 2
Possibilities for thousand place’s digit = 1
∴ Number of favourable outcomes = 2 x 3 x 2 x 1 = 12
Number of numbers formed by 1,2,3,4 (without repetitions) = 4!
∴ Required probability =
=