How do I add probabilities? Say I have 23% chance of A, and 48% chance of B, what are the chances of either? I used to think I would just add the probabilities, intuitively...then I came across problems where it sums to greater than 100%, but it's not certain. If you think like I used to think, this abstract example won't help you. So I'll give a descriptive version below. For anyone who can explain it to me, feel free to skip the next part:

Say Jimmy wants to destroy an unwanted statue. From research on statue destruction, he believes there is a 95% chance that the statue will be destroyed if he places it in front of the train. He also knows from research that if he puts a rope around it and drops it from a height, the force of the snap back will break the statue in half. He reasons that he can put a rope around it then attach that rope to the tracks, so that when the train comes, the snapping force will apply with the same destructive probability that the research cites - 96%. If the statue isn't destroyed, Jimmy is going to have to take care of the pieces, which will be a lot of work, so Jimmy wants to know what he's getting into. I wonder if there a way to combine the probabilities for an overall probabiltiy given that both apply?