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Difficult Probability Question
5 persons A, B,C, D, E sit randomly around a roundtable. The probability that A does not sit next to B is ____
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- 知足常樂Lv 77 年前最愛解答
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WLOG (Without Loss of Generality), you can fix A first.
Now, there are four seats remaining for four persons.
For B to choose out of the four seats, there are 2 places which satisfy your need (that is, A does not sit next to B).
Therefore, the required probability is 2/4 = 1/2.
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