Find the probability

The probability of John passing his Chemistry course is 0.75. The probability of John passing his Physics class is 0.8. If the probability of John passing both courses is 0.60, what is the probability that John will pass either his Chemistry or Physics course?

OPTIONS

• 0.75
• 0.8
• 0.6
• 0.95

ANSWER

0.95

EXPLANATION

This problem is a classic case of the additive law of probability, which is applied to the union of events. The probability that John passes either Chemistry or Physics is the union of the 2 events. The probability of 2 events A and B occurring is given by the addition rule, which is: P(A U B) = P(A) + P (B) – P(A ∩ B) The correct answer is 0.75 + 0.80 – 0.60 = 0.95