Here are all possible rolls of two dice: In[1]:= X = Flatten [Table [j + k, {j, 1, 6), {k, 1, 6)]] Out[1]= {2, 3, 4, 5, 6, 7, 3, 4, 5, 6, 7, 8, 4, 5, 6, 7, 8, 9, 5, 6, 7, 8, 9, 10, 6, 7, 8, 9, 10, 11, 7, 8, 9, 10, 11, 12} Given that a random roll is > 10, you can see by direct counting that the probability that the roll is 12 is - In [2]:= Y = Select [X, #1 >= 10 & ] Out[2]= [10, 10, 11, 10, 11, 12} Get the same result using the conditional probability formula