a fair die is rolled. what is the probability of rolling a 3 or a 6?

There are 6 possible outcomes when rolling a fair die: {1, 2, 3, 4, 5, 6}.

Out of these 6 outcomes, only 2 outcomes are favorable (rolling a 3 or a 6).
Therefore, the probability of rolling a 3 or a 6 is 2/6, which can be simplified to 1/3.