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Assume that a person can be born on a Monday with probability 1/3 and with equal probability any other day of the week. What is the probability that among 4 randomly selected people, two were born on the same day and the other two in two other days (for instance, two on Tuesday, one on Saturday and one on Friday)?

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    $\begingroup$ What have you tried? Note: you should clarify whether or not something like "two Tuesdays and two Thursdays" is a success or a fail. $\endgroup$ – lulu Oct 1 '18 at 11:15
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    $\begingroup$ As a general hint: because the days are not-equiprobable I'd split it up into cases. First suppose nobody was born on Monday, then suppose that the pair was Monday, then suppose that one of the non-pair was Monday. $\endgroup$ – lulu Oct 1 '18 at 11:16
  • $\begingroup$ There is only one pair soif two monday then the other 2 must be also diffenet such as Tuesday and Wednesday ive tried to split into cases but i cant find the finall answer note that i have the final answer which is 0.521 $\endgroup$ – Mohamad Abousaleh Oct 1 '18 at 11:30
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    $\begingroup$ Well, it's hard to help without seeing your work. That method should go through so I expect you just have an algebraic error. Please edit your post to show your work. $\endgroup$ – lulu Oct 1 '18 at 11:36

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