An unprepared student makes random guesses for the ten true-false questions on a quiz. Find the probability that there is at least one correct answer.

Answer 1

The probability for at least one correct answer, P(X>=1) is the same as probability of not getting ALL wrong answers or 1-P(X=0).
P(X=0) is getting every one wrong, with a probability of (1/2)^n, where n is the number of questions guessed.

Answer 2

0.999