What is the probability that if you roll two fair, standard six-sided dice, the difference between the two numbers rolled will be 0? Express your answer as a common fraction.
The first die can be anything. There's a 1/6 chance that the second die will match it.
Another way of saying it is that there are 36 possible combinations. Six of them are doubles. 6/36 = 1/6
1,1 1,2 1,3 1,4 1,5 1,6
2,1 2,2 2,3 2,4 2,5 2,6
3,1 3,2 3,3 3,4 3,5 3,6
4,1 4,2 4,3 4,4 4,5 4,6
5,1 5,2 5,3 5,4 5,5 5,6
6,1 6,2 6,3 6,4 6,5 6,6
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