1987 AMC 12 第 5 题

先试着解答 1987 AMC 12 第 5 题,然后核对你的答案与精心整理的解答,解答来自 LIVE by Po-Shen Loh。你也可以参加完整限时模拟考试、查看全部 1987 AMC 12 解答,或核对答案。

所有题目均经美国数学协会(MAA)官方合法授权使用。

5.

一名学生记录了一组测量值的精确百分比频数分布,如下表所示。然而,学生忘记标明测量值的总数 NN。NN 的最小可能值是多少?
测量值 百分比频数
00 12.512.5
11 00
22 5050
33 2525
44 12.512.5
100100
A student recorded the exact percentage frequency distribution for a set of measurements, as shown below. However, the student neglected to indicate N,N, the total number of measurements. What is the smallest possible value of N?N?
measured value percent frequency
00 12.512.5
11 00
22 5050
33 2525
44 12.512.5
100100
55
88
1616
2525
5050
答案:B
知识点:percentage frequency整除性sample size
小提示:
将每个非零百分比写成总数的最简分数
Express each nonzero percentage as a reduced fraction of the total
大提示:
由此得到的每个频数都必须是整数
Every resulting frequency must be a whole number
解答:
由于 12.5%=1812.5\%=\frac{1}{8},总数 NN 必须能被 88 整除。取 N=8N=8 时,各频数为 1,0,4,2,11,0,4,2,1,均为整数。因此,最小可能总数为 88。
所以正确答案是 B。
Since 12.5%=18,12.5\%=\frac{1}{8}, the total NN must be divisible by 8.8. Taking N=8N=8 gives frequencies 1,0,4,2,1,1,0,4,2,1, all whole numbers. Thus the smallest possible total is 8.8.
Therefore the correct answer is B.
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