（1）A的发生概率为0.6，B发生的概率为0.5，问A,B都不发生的最大概率？
请问P（A交B）=？
A不发生的概率为0。4，B不发生的概率为0。5，
（2）if you tossed a coin three times, what's the probability that you get the same side all three times.
请问在何种情况下用加法法则？
（3）袋中有a只白球，b只红球，依次将球一只只摸出，不放回，求第K次摸出白球的概率
（4）4本不同的书分给2人，每人2本，不同的分法有多少种？答案为C42 ，为什么不是 2C42 ，先把书分成两堆，然后在两个人分？[em12][em12][em12][em12][em12]作者: pgclt 时间: 2002-10-17 05:30
（1）A的发生概率为0.6，B发生的概率为0.5，问A,B都不发生的最大概率？
请问P（A交B）=？
A不发生的概率为0。4，B不发生的概率为0。5，
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There's been some discussion about this kind of problem. The key issue is whether A and B are dependent on each other. If no inter-dependency, I think A,B都不发生的最大概率 is 0.4. A,B都不发生的概率 is 0.5*0.4 = 0.2.
（2）if you tossed a coin three times, what's the probability that you get the same side all three times.
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(1/2)^3 for a designated side: head or tail. If just say same side. 2*(1/2)^3 .
（3）袋中有a只白球，b只红球，依次将球一只只摸出，不放回，求第K次摸出白球的概率
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I don't think such probelms will appear in real exam. trying to solve:
K=1, P1 = [a/(a+b)];
K=2, P2 = [a/(a+b-1)] or [(a-1)/(a+b-1)] depending on first one is red or white.
K=3, P3 = [a/(a+b-2)] or [(a-1)/(a+b-2)] or [(a-2)/(a+b-2)] again depending on first two balls are red or white.
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