求助！！！prep一道数学多个答案。

shiyadan · 发表于 2011-7-26 16:33:34

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In a certain year, the difference between Mary's and Jim's annual salaries was twice the difference between Mary's and Kate's annual salaries. If Mary's annual salary was the highest of the 3 people, what was the average (arithmetic mean) annual salary of the 3 people that year?

(1) Jim's annual salary was $30,000 that year.

(2) Kate's annual salary was $40,000 that year.

方法一：答案为B
由题意得知M-J=2(M-K)
M+J=2K　代入 = =K
(1) 有2个未知
(2) 代入上面简化的算式得到.

方法二：答案为A
由题意知M-J=X
M-K=2X
(M+J+K)/3=(M+M-X+M-2X)/3=(3M-3X)/3=M-X=J
(1) 代入上面简化的算式得到.
(2) 有2个未知

原题的答案为B，各位高手看看应该选A、B还是D？

fresh7129 · 发表于 2011-7-26 16:43:25

你的方法二是错误的吧，看看题，M-J=2(M-K)
你的第二个方法，弄成M-K=2(M-j)

答应应该是正确的，B

shiyadan · 发表于 2011-7-26 17:27:56

哦，大脑抽着了！万分感谢啦！！！祝好！！！

求助！！！prep一道数学多个答案。

所属分类: GMAT考试

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