In an insurance company, each policy has a paper record and an electric record. For those policies having incorrect paper record, 60% also having incorrect electric record; For policies having incorrect electric record, 75% also having incorrect paper record. 3% of all policies have both incorrect paper and incorrect electric records. If we randomly pick out one policy,what’s the probability that the one having both correct paper and correct electric records?

(A) 0.80 (B) 0.94 (C) 0.75 (D) 0.88 (E) 0.92

解：设总数为x，设incorrect paper record有y, incorrect electric record有z，则：

x·y·60%=3%·x y=5%

x·z·75%=3%·x z=4%

则，两者至少有一个错误的百分比为5% 4%-3%=6%，所正确答案为94%

14. There are 1200 respondents to a poll, each favoring their preference for candidates A,B, and C. 54% favored A, 48% favored B, and 42% favored C, and there is 30% favored both A and B. what’s the largest possible number of respondents favoring C, but not C&B, nor C&A?

(A) 25% (B) 30% (C) 28% (D) 38% (E) 40%

解：A和B的并集为：54% 48%-30%=72%，所C为28%.