SOLUTION: A quiz has 4 multiple-choice questions. Each question has 5 choices, 1 being correct and the other 4 being incorrect. Suppose you guess on all 4 questions. What is the probability

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Question 1042802: A quiz has 4 multiple-choice questions. Each question has 5 choices, 1 being correct and the other 4 being incorrect. Suppose you guess on all 4 questions. What is the probability of getting 3 questions right?
Found 2 solutions by ikleyn, MathTherapy:
Answer by ikleyn(52776) About Me  (Show Source):
Answer by MathTherapy(10551) About Me  (Show Source):
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A quiz has 4 multiple-choice questions. Each question has 5 choices, 1 being correct and the other 4 being incorrect. Suppose you guess on all 4 questions. What is the probability of getting 3 questions right?
Use the BINOMIAL PROBABILITY formula: %22+%22%5Bn%5DC%5Bs%5D+%2A+p%5Es+%2A+q%5E%28n+-+s%29

Probability of getting EXACTLY 3 correct: