Six persons throw for a stake, which is to be won by the one who first throws head with a coin: if they throw in succession, find the chance of the fourth person.
Six persons throw for a stake, which is to be won by the one who first throws head with a coin: if they throw in succession, find the chance of the fourth person.
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52张扑克牌,没有大小王,无放回地抽取两次,则两次都抽到A的概率为______;已知第一次抽到的是A,则第二次抽到A的概率为______.
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从一副混合后的扑克牌(52张)中,随机抽取1张,事件A为“抽得红桃K”,事件B为“抽得黑桃”,则概率P(A∪B)= ________(结果用简分数表示).