A high school probability problem

Release method of * * *: a (5,5) =120.

These five numbers are the same: 1.

Three Numbers Same: Select the same three numbers C (5,3) 3)= 10/0. After the same number is determined, for example, 1, 2, 3 are the same, then the No.5 ball can only be placed in the No.4 box, and the No.4 ball can be placed in the No.5 box. There is only one way to play. So it is c (5,3) *1=10.

Two numbers are the same: give the same two numbers c (5,2) 2)= 10/0. After the same number is determined, for example, 1 is the same as 2, then it is assumed that box No.3 contains ball No.4, box No.4 can't contain ball No.3, only ball No.5, and box No.5 contains ball No.3.. If box 3 puts ball 5, box 4 can only put ball 3 and box 5 can only put ball 4. There is only one way to play. So it is c (5,2) * 2 = 20.

The probability is (1+10+20)/120 = 31120.