<PRE><B>Question 421808</B>
A multiple choice exam has ten questions and each question had 4 possible answers. In each case only 1 of the 4 possibilities is correct. 
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Billy fills out an answer sheet by simply guessing without even reading the questions.
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Binomial with n = 10 and p = 1/4
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What is the probability that he will get 100% on the exam? 
P(x = 10) = (1/4)^10 = 9.5367x10^-7
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What is the probability that he will get 90% on the exam? 
P(x = 9) = 10C9*0.25^9*0.75 = 2.8610x10^-5
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What is the probability that he will get at least an 80% on the exam?
P(x = 8) = 10C8*0.25^8*0.75^2 = 3.8624x10^-4
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Cheers,
Stan H.
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