用实例告诉你GRE数学疑难题型解题技巧

>>GRE数学考试技巧：用实例告诉你GRE数学疑难题型解题技巧

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例题1：more than twice

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 followingamounts 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。

例题2：dollar amount

If the dollar amount of sales at Store P was $800,000 for 2006, what was the dollar amount of sales at that store for 2008 ?

A $727,200

B $792,000

C $800,000

D $880,000

E $968,000

直接算，800000*(1+10%)*(1-10%)=792000，即B

2)At Store T, the dollar amount of sales for 2007 was what percent of the dollar amount of sales for 2008 ?

Give your answer to the nearest 0.1 percent.___________%

直接算，1/(1-8%)=108.7%(约等于)

3)Which of the following statements must be true?

Indicate all such statements.

A For 2008 the dollar amount of sales at Store R was GREater than that at each of the other four stores.

B The dollar amount of sales at Store S for 2008 was 22 percent less than that for 2006.

C The dollar amount of sales at Store R for 2008 was more than 17 percent greater than that for 2006.

本题A选项一看到就可以排除了，涉及到两个店的绝对量的比较，这个不确定，没有告诉绝对值。B选项是把两个增长的比例简单地算术相加。肯定错了。所以C肯定是对的了。。通过计算也的确是对的。

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