In a nationwide poll, N people were interviewed. If 1/4 of them answered “yes” to question 1, and of those, 1/3 answered “yes” to question 2, which of the following expressions represents the number of people interviewed who didn’t answer yes to both questions?
正确答案是1-1N/4*3N/4=11N/12
看到答案才知道是求没有两道题同时答YES的人数。
而之前自己的理解是didn’t answer yes to both questions = 对两道题都没有答yes，也就是说对两道题都答了NO
people interviewed who didn’t answer yes to both questions are the people who answered No to both questions or answered no to only one of the questions.
Answer yes to both question means Yes for 1 and Yes for two.
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发表于 2011-3-5 00:30:57
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