gre数学：5道难题解答2_GRE数学

gre数学：5道难题解答2

　　考点：凑的方法，要掌握好选数的区别性，比如此题中，五位数的头和尾如果都是单数，那么差值必定是双数，无法排除A,D选项。而用严谨的方法做题时，要大胆假设，不要担心未知数个数多，就不敢假设。最后都可以消掉的。

　　7.比大小

　　解答：1/=100/97 ; 1.03=103/100 大于1的分数，上下同时加一个数，变小A

　　考点：分数比大小

　　8.The original value of machine X is V dollars, while the original value of machine Y is 2V dollars. Both machines depreciate in value at a constant rate of 10 percent of their original value per year.

　　翻译：X机器的原价为V，Y机器的原价为2V，每年都贬值原价的10%，比大小

　　解答：A= V0.9^3

　　B= 2V 0.9^6

　　 B/A = 20.9^3 = 1.458 1 BA 选B

　　考点：对贬值概念的理解

　　9.If n is an odd integer, which of the following in the square of the next larger odd interger?

　　A. n^2+1

　　B. n^2 + 4

　　C. n^2 + 2n +1

　　D. n^2+4n+4

　　E.n^2+n+1

　　翻译：n是偶整数，那么下列哪么是邻近的比n大的偶整数的平方

　　解答^2 = D

　　10.If 55 percent of a group of people have brown hair and 80 percent of the same group do not have red hair, what fraction of those who do not have brown hair have red hair? 分页标题#e#