The probabilities that Ade and Bisi will pass an examination are 2/3 and 3/4 respectively. Find the probability that only one of them passes the examination.

P(only Ade passes) = (2/3)(1/4) = 2/12. P(only Bisi passes) = (1/3)(3/4) = 3/12. P(exactly one passes) = 2/12 + 3/12 = 5/12. A common error is computing P(both pass) = 1/2 or ignoring the complementary probabilities.