[求助]陈向东 逻辑95页第7题

7  The Wheat Farmers Alliance, a political action commitee, attracts 70 percent of its contributors from an advertisement requesting contributions placed only in the September, October, and November issues of the Grange Report, a monthly newsletter for wheat farmers. The president of the Wheat Farmers Alliance, to increase the number fo contributors, decides to advertise in each of the monthly issues of the Grange Report. She expects that, the number of contributors will be increased to at least double the present number.

Which of the following, if true, would most strongly support the president's expectation?

(A) The September, October, and November advertisements were noticed by fewer than one-third of those readers of the Grange Report who would be willing to contribute to the Wheat Farmers Alliance.

答案：A

为什么A是答案呢？怎么才能推出其中的逻辑数学关系？

题干说：WFA只将其广告刊登在GR的九、十、十一月的期刊上。这些广告吸引了70％的contributor。则WFA的president决定在GR的每一期上都刊登广告。认为这样做会至少使目前的数目翻一番。

A说：刊登于九、十、十一月的广告只被少如三分之一的愿意contribute to WFA的GR的读者所注意。

所以说如果三个月仅仅能引起三分之一潜在客户的注意，那么如果十二个月都刊登广告，那么就有可能引起所有潜在客户的注意。那就是contributor会增加三倍，也正如那个president所预料的，contributors的数目至少会翻一番。