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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.

参*：A

题目解析：prime number = 质数，比24大的质数中最小的是29，比28小的质数中最大的是23，因此选A。

2. Quantity A：54% of 360

Quantity B：150

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.

参*：A

题目解析：不用去算54%*360，只要知道360的一半是180，A超过了，所以比B大，因此选A。

3. When the decimal point of a certain positive decimal number is moved six places to the right, the resulting number is 9 times the reciprocal of the original number. What is the original number?

参*：如果一个数的小数点右移6位，那么结果将是这个数的倒数的9倍.

设这个数为x，列出等式：1000000x=9/x，解得x=0.003

4. 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

参*：E

题目解析：笨办法是自己画坐标轴然后计算，但仔细观察四组坐标会发现各有两组的某一个值相同，因此实际构成一个长方形。最后周长为34。

5. Three pumps, P, R, and T, working simultaneously at their respective constant rates, can fill a tank in 5 hours. Pumps P and R, working simultaneously at their respective constant rates, can fill the tank in 7 hours. How many hours will it take pump T, working alone at its constant rate, to fill the tank?

A. 1.7

B. 10

C. 15

D. 17.5

E. 30

正确答案：D

题目解析：根据题目条件，设三个泵各自速率为p,r,t。列出等式：(p+r+t)*5=(p+r)*7，算出p+r=2.5t，然后设T独自工作需要时间为x，列出等式：(p+r)*7=t*x，代入上个式子的结果，x=2.5*7=17.5。

GRE数学代入解题法介绍

所谓代入解题法，就是指反过来根据选项来反推题目解题的方法。简单来说，把选项代入计算验证的方法，就使用到了代入解题的思路。对于许多复杂的，正面解决需要大量计算的题目来说，代入解题法不仅不会消耗大家的考试时间，反而会节省下不少时间，大幅度提高解题速度，使用得当甚至能带来较大幅度的提分。