考生在备考gre数学的时候难眠会遇见叫难的题目，考生一时间答不出来，在通过答案解析之后，考生可以重新获取新的知识，今天小编为大家带来的就是gre数学试题解析版。
.Each employee of a certain company is in either Department X or Department Y, and there are more than twice as many employees in Department X as in Department Y. The average (arithmetic mean) salary is $25,000 for the employees in Department X and is $35,000 for the employees in Department Y. Which of the following amounts could be the average salary for all of the employees in the company?
Indicate all such amounts.
A $26,000
B $28,000
C $29,000
D $30,000
E $31,000
F $32,000
G $34,000
本题我们要注意到题目中的more than twice的字眼，我们当做twice算的时候，结果是(25000*2+35000)/3约等于28333，因为有more than，所以选的答案要么是比前面这个数大，要么小，又由于more的是X部门的，那么肯定会将平均工资给拉低了，因此，选比前面那个数小的答案，AB都可以了。。
18.The range of the heights of the female students in a certain class is 13.2 inches, and the range of the heights of the male students in the class is 15.4inches.
Which of the following statements individually provide(s) sufficient additional information to determine the range of the heights of all the students in the class?
Indicate all such statements.
A The tallest male student in the class is 5.8 inches taller than the tallest female student in the class.
B The median height of the male students in the class is 1.1 inches greater than the median height of the female students in the class.
C The average (arithmetic mean) height of the male students in the class is 4.6 inches greater than the average height of the female students in the class.
分析：在数轴上我们可以画出一段表示女生身高范围，另一段表示男生身高范围，
A选项告诉我们的是男生最高的比女的最高的高5.8inch，那么我们就可以确定两段的相对位置了，因此总的身高范围就可以确定了。选项A就是对的了。
B选项，由于没有告诉我们男女生的人数，所以这个是无法确定的
C选项，这个选项跟上面的B差不多，没法确定。附上OG的解答，以作参考：
Choice B provides information about one of the centers of the data—the median; it does not say anything about how spread out the data are around that center. You are given that the median height of the males is 1.1 inches greater than that of the females. First note that it is possible for two different sets of data to have the same median but have very different ranges. Choice B gives the difference between the medians of the male heights and the female heights, without giving the actual medians. However, even if you knew the medians, the fact that the ranges can vary widely indicates that the range of the heights of the entire class can also vary widely. It is possible to construct examples of heights of students that satisfy all of the information in the question and in Choice B but have different ranges for the heights of the entire class. Here are two such examples, each of which has only three females and three males. Although the examples are small, they illustrate the fact that the range of the heights of the entire class can vary. In both examples, the range of female heights is 13.2, the range of male heights is 15.4, and the difference between the median heights is 1.1 inches.
Example 1
Female heights: 50.0 56.6 63.2 which have a median of 56.6
Male heights: 50.0 57.7 65.4 which have a median of 57.7
Range of heights of entire class: 15.4
Example 2
Female heights: 50.0 56.6 63.2 which have a median of 56.6
Male heights: 51.0 57.7 66.4 which have a median of 57.7
Range of heights of entire class: 16.4
Therefore, Choice B does not provide sufficient additional information to determine the range of the heights of the entire class.
Choice C provides information about another center of the data—the average. You are given that the average height of the males is 4.6 inches greater than that of the females. However, like Choice B, the statement gives no information about how spread out the data are around that center. Again, it is possible for two different sets of data to have the same average but have very different ranges. Examples similar to the two examples above can be constructed that satisfy all of the information in the question and in Choice C but have different ranges for the heights of the entire class. Therefore, Choice C does not provide sufficient additional information to determine the range of the heights of the entire class.
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