其实应该不难啦 但.... Keno is a favorite game in casinos, and similar games are popular with the states that operate lotteries. Balls numbered 1 to 80 are tumbled in a machine as the bets are placed, then 20 of the balls are chosen at random, Players select numbers by marking a card. The simplest of the many wagers available is "Mark 1 number" . You payoff is $3 on a $1 bet if the number you select is one of those chosen. Because 20 of 80 numbers are chosen, your probability of winning is 20/80, or 0.25. (a) What is the probability distribution ( the outcomes and their probabilities) of the payoff X on a single play? (b) What is the mean payoff? (c) In the long run, how much does the casino keep from eavh dollar bet? 题目有点长 不知道有没有人可以帮忙解答呢？ 谢谢！ -- --

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