prep 1-58

Kath1985 · 发表于 2011-3-15 11:31:51

58.7090-!-item-!-187;#058&005463

In the graduating class of a certain college, 48 percent of the students are male and 52 percent are female.In this class 40 percent of the male and 20 percent of the female students are 25 years old or older.If one student in the graduating class is randomly selected, approximately what is the probability that he or she will be less than 25 years old?

(A) 0.90

(B) 0.70

(C) 0.45

(D) 0.30

(E) 0.25
答案B
我的方法不是1-0.296=0.7
而是由題目的male0.4和female0.2反推出小於25歲的機率為0.6*0.48+0.8*0.52
請問我的方法對不對呢
[attachimg=331,278]85439[/attachimg]

softheart · 发表于 2011-3-15 15:47:06

我觉得2个方法都对.

abysmalveil · 发表于 2011-3-15 18:45:23

两个方法都一样～

prep 1-58

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