Question 409310: An unprepared student makes random guesses on a 5 question true-false examination. What is the probability that she/he will answer at least one question correctly?
Answer by richard1234(7193)   (Show Source):
You can put this solution on YOUR website! The probability that he/she answers at least one correct is equal to 1 minus the probability that he/she answers none of them.
There are five questions, and two choices each, so 32 ways to answer all the questions. The only way to answer none of them correctly is to guess each question incorrectly, so the probability this occurs is 1/32. Subtracting this from 1, the probability that he/she gets at least one correct is 31/32.
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