mutually exclusive

In probability theory, describing two events that cannot happen together. For example, it is not possible to throw a 6 and a prime number on the same die at the same time. The probability that both events will happen is zero. The probability that either one or the other of two mutually exclusive events will happen is the sum of their separate probabilities. The addition rule is

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

So when a die is thrown, the probability of throwing a 6 or a 3 is: P(6 or 3) = P(6) + P(3) = 1/6 + 1/6 = 2/6 or 1/3.

If a person buys 5 tickets out of 100 in a lottery with only one winning ticket, the chance of winning the prize is 0.01 + 0.01 + 0.01 + 0.01 + 0.01 = 0.05.