SOLUTION: in an exam student is to answer 10 of 13 questions find the probability that: he must answer the first two question? he must answer the first or the second but not both? he must

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Question 925723: in an exam student is to answer 10 of 13 questions find the probability that: he must answer the first two question?
he must answer the first or the second but not both?
he must answer exactly 3 of the first 5 questions?
he must answer at least 3 of 5 question?

Answer by ewatrrr(24785) About Me  (Show Source):
You can put this solution on YOUR website!
13 Questions: 10A, 3(not answered)
P(answering first two) = %2810%2F13%29%289%2F12%29
P(first or the second but not both) = %2810%2F13%29%283%2F12%29+%2B+%283%2F13%29%2810%2F12%29
P(exactly 3 of the first 5 questions) = %2810C3%29%283C2%29%2F13C2%29
P( 3 0r 4 0r 5) =