New Balls and Old Balls

6/10StatisticsprobabilityCasework

Problem

Of 55 table-tennis balls, 33 are new and 22 are old. For each match, 22 balls are drawn, used, and returned (used balls become old). Let ξ\xi be the number of new balls drawn in the second match. Find E(ξ)\mathbb{E}(\xi).

Answer

Solution

Difficulty6/10
TopicsStatistics, probability, Casework

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