The probability that an event A occurs is P(A) = 0.3 . The event B is independent of A and P(B) = 0.4 .

Question

a) Calculate P(A or B or both occur) .

Thanks in advance for the help!

Answer 1

Thanks for the reply! I get that the "a)" might have made it seem like a multiple choice question, but it's not, you gotta calculate the answer using the info given above. According to the answers, it's supposed to be 0.58, but what I need to know is how to get there.

I've always thought that "or" means you add the probabilities up. So that would mean 0.4 + 0.3 + 0.4 x 0.3 = 0.82 but that obviously isn't the answer. Could someone explain how to get 0.58?

Thanks in advance

Answer 2

P(A) or (B) or (both) = P(A) + P(B) - [P(A) * P(B)]