Question

On a 9 question multiple-choice test, where each question has 5 answers, what would be the probability of getting at least one question wrong?

Answer 1

Answer:

P(at least one wrong) = 1- P(all correct) =1-.25^6=1-1/4096=4095/4096. This assumes that the answers are picked at random. This kind of question is always the complement of an extreme binomial outcome.