问一个PREP上的ps，求助啊

norlanzhang · 发表于 2012-3-1 18:38:53

Ann	$450,000
Bob	$360,000
Cal	$190,000
Dot	$210,000
Ed	$680,000

The table above shows the total sales recorded in July for the 5 salepeople at Acme Truck Sales. It was discovered that one of Cal's sales was incorrectly recorded as one of Ann's sales. After this error was corected, Ann's total sales were still higher than Cal's total sales, and the median of the 5 sales totals was $330,000. What was the value of the incorrectly record sale?
A. $30,000
B. $48,000
C.$90,000
D. $120,000
E. $140,000
为什么选的是D选项啊？

treewing929 · 发表于 2012-3-1 18:52:52

推論
只有A 同 C 錯. Median 是 33萬, 所以a或c 33萬
如果c, 那麼 a 便是 31萬, 但題目說更正後 a 依舊大過c, 所以a 是33萬, 而錯是45萬減33萬=12萬.

查理密 · 发表于 2012-3-1 19:04:02

题目说的是C的一笔销售额记到了A的销售额上，如果更正此错误，那么五个数中位数变成了330.000，且A还是比C的销售额高。肯定是这两笔中有一笔变成了330.000啦：1.A的sale是330.0002,。C的sale是330.000
经过计算发现A的sale变330.000 错误账就是120.000，如果C的sale变330.000错误账就是140.000 C 33-19=14 A 45-14=31 31<33不符合题意啦! 所以选120.000

问一个PREP上的ps，求助啊

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