Addition Rule For Probabilities

The Addition Rule for Probabilities (ARFP is not, we repeat not, the sound a dog makes when vomiting) is the idea that the probability that event A or event B happens is the probability that event A happens plus the probability that event B happens...minus the probability that both events A and B happen.

In math-lish, it's P(A ? B) = P(A) + P(B) ? P(A ? B).

If we've got two random events (like the probability of getting that swipe right from two different potential mates/hook-ups), we can find the probability that one or the other gives us the internet thumbs-up by adding the individual probabilities that each swipes right minus the probability that they, uh...both look at our profile and want to see more.