Help, one more problem

First calculate the probability, q, that no two dice show the same number:

 

first die:  any number

second die:  prob 5/6 that it is different from first

third die:      prob  4/6 that it is different from first two

fourth die:    prob  3/6 that it is different from first three

fifth die:       prob  2/6 that it is different from first four.

 

Hence;  q = 5*4*3*2/6^4

 

Porbability, p, that at least two show the same number is p = 1 - q

 

p = 1 - 5*4*3*2/6^4             (You can crunch the numbers!).