How do you calculate theoretical probability?
Assume that each outcome is equally likely to occur.
The probability of the event
What is the probability of rolling a multiple of 3 when you roll a standard die once?
Since all outcomes are 1 through 6, we have the sample space
Since all multiple of 3 are 3 and 6, we have the event
Hence, the probability of rolling a multiple of 3 is
I hope that this was helpful.