Question 442721
Ok, so for P(A or B), if either P(A) happens or P(B) happens, then the outcome is true. So, we can write P(A or B) as  P(A) + P(B) if we are mutually exclusive.

If we are not mutually exclusive, we have to take away the probability of both A and B happening. So P(A or B) is  P(A) + P(B) - P(A and B).

Now for P(A and B), both A and B have to happen for the outcome to be true. So we have to account for the probability of A and then account for the probability of B. P(A and B) = P(A) * P(B). Provided that A has already happened.

Say you have a coin. The first time you flip it you have a 1/2 probability of getting heads. Let's say you flip it again, you still have a 1/2 probability of getting heads. As you add more probabilities, the ultimate probability is going to become slimmer and slimmer. In this case, you have a 1/4 chance of flipping heads 2 times.