In an insurance company, each policy has a paper record or an electric record, or both of them. 60 percent of the policies having incorrect paper record have incorrect electric record and 75 percent of the policies having incorrect electric record have incorrect paper record. 3 percent of all the policies have both incorrect paper and incorrect electric records. If we randomly pick out one policy, what is the probability that it is one having both correct paper and correct electric record? 【答案】94% 【思路】设总数为X policies，则既有非P又有非E为3%X；60%的非P中为非E，则非P为3%X/60%；75%的非E为非P，则非E为3%/75%，那么非P与非E一共有（3%X/60%+3%X/75%-3%X） ，那么P与E一共有X-（3%X/60%+3%X/75%-3%X），则其概率为[X-（3%X/60%+3%X/75%-3%X）]/X=94%
偶怎么觉得题目问的是p和E的交集的概率，但是好像答案给的是p&e并集的概率？请执教！作者: mialanhero 时间: 2004-6-7 14:20
any nn can help me?
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