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Message: <blockquote data-quote="zanharjabir" data-source="post: 4541528" data-attributes="member: 56443">A student returns to his apartment late at night to find that the exterior lights have been put out. He can’t see the 5 keys on his key-ring to distinguish one from the other and thus cannot identify his front door key. He feels for the lock and then randomly chooses a key and tries it in the lock. The darkness is so deep that he must randomly choose a key each time, with no guarantee that the same key will not be picked again, and he continues doing this until he picks the correct key.a.    What is the probability that he picks the correct key on the first try?b.    What is the probability that the first 5 tries are all wrong?</blockquote>

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