Re: [計量] PP2 PS-167
※ 引述《Q7 (T^T)》之銘言：
: 167.
: In a survey of 248 people, 156 are married, 70 are self-employed, and 25
: percent of those who are married are self-employed. If a person is to be
: randomly selected from those surveyed, what is the probability that the
: person selected will be self-employed but not married?
: (A) 1/8
: (B) 4/31
: (C) 117/248
: (D) 1/4
: (E) 31/117
: 答案是A = =
: 我算出來的答案是1/31 我真的想不透.....
: 我的算法是全體為248 25% married and self-employed 的人數為62
Percent 和 Fraction 其實就跟修辭一樣
x percent of A be (V) .......(by B)
所以 x% = A & B / A
25 percent of those who are married are self-employed
^^^^^^^^^^^^^^^^^^^^^ ^^^^^^^^^^^^^
25% = married & self-employed / married
所以應該是 156 * 25% = 39
70 - 39 = 31 31/248 = 1/8
: 70-62=8 這是be self-employed but not married的人數
: 8/248=1/31 這是被抽中的機率。
: 結果沒這答案= = 哪裡出錯了= =
: 懇請高手指點
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※ 編輯: dounts 來自: 111.248.207.173 (04/06 23:26)
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