Kevin rolls a 6 sided die what is the probability that he gets a number greater than 3 or a prime number

Let event A be the probability of getting a number greater than 3.
P(A) = 3/6
Let B be the probability of getting a prime number.
P(B) = 3/6
However 5 is common to both events.

A union B is the event A or B.


Therefore the probability that he gets a number greater than 3 or a prime number is 5/6.