作者SHAOCHU (月台上的观察员)
看板GRE
标题Re: [计量] 一题数学题
时间Sun May 10 12:53:43 2015
※ 引述《ghtmmm (圣艾修伯里)》之铭言：
: In a quality-control test, 50 boxes-each containing 30 machine parts-were
: examined for defective parts. The number of defective parts was recorded for
: each box, and the average (arithmetic mean) of the 50 recorded numbers of
: defective parts per box was 1.12. Only one error was made in recording the 50
: numbers: "1" defective part in a certain box was incorrectly recorded as "10".
: Quantity A
: The actual average number of defective parts per box
: Quantity B
: 0.94
: 答案是C
: 这题看好久还是不知道题目在问甚麽...
大意为：
有50个箱子，每个箱子中有30个机台零件。将这些零件送检，
得到每个箱子内含缺陷的零件数平均为1.12(个/箱)，
其中有1个缺陷被误植为10个。
[解]
误植後的总缺陷数为1.12*50=56(个)。
被误植的零件其缺陷数多算了9(=10-1)个，所以确切的总缺陷数为56-9=47(个)，
故每箱实际平均缺陷零件数为(47/50)=0.94 --- 亦即为Quantity A。
则Quantity A = Quantity B，
选C。
A2GMAT KH
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※ 编辑: SHAOCHU (180.177.217.26), 05/10/2015 12:54:21