SOLUTION: If eight different books are arranged at random in a shelf, what is the probability that a certain pair of book a. Will be beside each other? b. Will not be together?

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Hi,

eight different books 8! total ways of arranging on shelf

thinking OF A 'PAIR' AS ONE UNIT

P(beside each other) = 7!/8!

P(not be together) = 1 - P(together) = 1- 7!/8!