Re: [問題] PP 數學請教
※ 引述《KMI (無奈)》之銘言：
: DS: 剛剛模考做到
: A certain one-day seminar consisted of a morning session and an afternoon
: session. If each of the 128 people attending the seminar attended at least
: one of the two sessions,
: how many of the people attended the morning session only?
: 1) 3/4 of the people attended both sessions.
: 2) 7/8 of the people attended the afternoon session.
: 答案: B
畫圈圈圖會比較好理解
學生有三種(M: morning session; A:Afternoon session)
I. M but not A
II. both M & A
III. A but not M
1)只知道M & A交集的人數 --> not sufficient
2)知道I+II=7/8*128=112,又題目給說所有的學生=I+II+III
所以可以得知attend the M only的人數有128-112=7人
---> sufficient!
Therefore, choose the answer B
: A certain city with a population of 132,000 is to be divided into 11 voting
: district, and no district is to have a population that is more than 10%
: greater than the population of any other district. What is the minimum
: possible population that the least populated district could have?
: 1. 10700
: 2. 10800
: 3. 10900
: 4. 11000
: 5. 11100
: 答案: D
題目重點"任何一個district的人均不大於另一個district人數的10%"
--->即最多和最少人數的district差10%
設這11個district中人數最小者有x人
最極端的情形...就是另外10個district人數均是1.1x
則1.1x*10+x = 132000
求解得出x=11000
Choose answer D
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09/27 21:41, , 1F
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