Question

After rolling a 6-sided number cube once, what is the probability of rolling a 1 or a 4? P(1 or 4)

Answer 1

In general, you have the following formula:
P(A or B) = P(A) + P(B) - P(A and B)

The probability of rolling a 1 AND a 4 is 0, since you can only get one number in a single roll (i.e. the events are mutually exclusive).

What's the probability of rolling a 1, and the probability of rolling a 4? (Find P(1) and P(4), then add them up.)