A die is rolled 4 times. find the probability of
two 1's, one 2, and one 3.
The probability of rolling the sequence 1,1,2,3 is
.
But that sequence could be in any order, and the
number of ways of arranging 1,1,2,3 since the
two 1's are indistinguishable, is
Therefore the desired probability is
.
Edwin