Board Thread:General Discussion/@comment-6182229-20130207070333/@comment-6133056-20130208141855

That's how it works. Quoted from Wiki:

Mutually exclusive

If either event A or event B or both events occur on a single performance of an experiment this is called the union of the events A and B denoted as P(A U B). If two events are mutually exclusive then the probability of either occurring is

P(A or B) = P(A U B) = P(A) + P(B)

For example, the chance of rolling a 1 or 2 on a six-sided die is

P(1 or 2) = P(1) + P(2) = (1/6) + (1/6) = (1/3)

Or in this case, the chance of getting a 5* is

P(69/10000) x 62 = 0.62 x 62 = 42.78%