Play poker with 5 dice and find the porbability that hand is four of a kind

Prob (getting for 1's in first 4 throws) = (1/6) ^2 * 5/6 = 5 / 7776

There are 5 ways to get 4 1's so this Probability is 25/7776

so probability of getting 2 - 6 4 times = 5 * 25 / 7776

= 125 / 7776 = Prob (4 of a kind)