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GRE数学培训_GRE数学真题解析(精选一)
时间:2020-07-09
来源:朗思教育
作者:Eric chen
1.
Quantity A
The least prime number greater than 24
Quantity B
The greatest prime number less than 28
A Quantity A is greater.
B Quantity B is greater.
C The two quantities are equal.
D The relationship cannot be determined from the information given.
【解析】A
质数是指只能够被1和它本身整除的正整数
A:大于24最小的质数就是29
B:小于28最大的质数就是23
2. From 2011 to 2012, Jack`s annual salary increased by 10 percent and Arnie`s annual salary decreased by 5 percent. If their annual salaries were equal in 2012, then Arnie`s annual salary in 2011 was what percent greater than Jack`s annual salary in 2011 ?
Give your answer to the nearest 0.1 percent. _____%
【解析】15.8
设2011年Jack和Arnie的年收入分别是x和y
那么2012年Jack和Arnie的年收入分别就是x*(1+10%)=1.1x和y*(1-5%)=0.95y
2012年两人的年收入相等,所以1.1x=0.95y,可以解得y≈1.158x,即y比x高出15.8%
3. In 1993 a card company that sold 40 percent of the Mother`s Day cards that year priced its cards for that occasion between $1.00 and $8.00 each. If the revenue from sales of the company`s Mother`s Day cards in 1993 was r million dollars, which of the following indicates all possible values of r ?
A 155 < r < 1,240
B 93 < r < 496
C 93 < r < 326
D 62 < r < 744
E 62 < r < 496

【解析】E
1993年该公司销售了当年40%的母亲节贺卡,每张贺卡的价格在1美元到8美元之间,根据右边的图形可知,1993年母亲节贺卡总量是155million,其40%的就是155*40%=62million
那么这部分的销售总收入介于62million和62*8=496million之间。
4. A group of 5,000 investors responded to a survey asking whether they owned stocks and whether they owned bonds. Of the group, 20 percent responded that they owned only one of the two types of investments. If r is the number of investors in the group who owned stocks but not bonds, which of the following represents the number of investors in the group who owned bonds but not stocks, in terms of r ?
A 5,000
B 1,000 – r
C r – 1,000
D 1,000r
E (0.2)*(5,000 – r)
【解析】B
设持有股票的是A集合,持有债券的是B集合
根据题意可得只属于其中一个集合的是A+B-2*A∩B=5000*20%=1000;
只属于A集合的是r,r=A-A∩B;
需要求的是只属于B集合的,也就是B-A∩B=1000-r.
5. The 5 letters in the list G, H, I, J, K are to be rearranged so that G is the 3rd letter in the list and H is not next to G. How many such rearrangements are
A 60
B 36
C 24
D 12
E 6
【解析】D
指定位置型排列,优先排特殊的元素
G在第三位,只有一种方法;H不能和G相邻,那么H的排法有C(2,1)种;最后排剩下的三个字母的排列有A(3,3)种;
所以一共有C(2,1)*A(3,3)=12种排列方法。
6. From the 5 points A, B, C, D, and E on the number line above, 3 different points are to be randomly selected. What is the probability that the coordinates of the 3 points selected will all be positive?
A 1/10
B 1/5
C 3/10
D 2/5
E 3/5

【解析】A
从坐标轴可以看出是负数的有两个点A和B,是正数的有三个点C,D,E
如果要求选出来的三个点都是正数的话,只能是组合{C,D,E},只有1种;
而从该五个点当中随机选出三个点的组合数有C(5,3)种;
所以选到三个点都是正数的概率就是P=1/C(5,3)=1/10.
7. In the xy-plane, a quadrilateral has vertices at (-1, 4), (7, 4), (7,-5), and (-1, -5). What is the perimeter of the quadrilateral?
A 17
B 18
C 19
D 32
E 34
【解析】E
设这四个点分别就是A(-1, 4), B(7, 4), C(7,-5), and D(-1, -5)
那么AB=CD=8, BC=DA=9
四边形ABCD的周长就是2*(8+9)=34.
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