分享五道高频GRE数学试题答案及解析

　　GRE数学部分对于考生来说是难度相对较低的，考生也期望着能够在这个部分表现出色拿到高分满分以提升总成绩。本文将GRE 数学各大高频考点题型的具体讲解和解题思路剖析，确保考生不在简单数学部分意外失分，顺利拿到高分满分！
　　 题目1. A box contains 100 balls, numbered from 1 to 100.If three balls are selected at random and with replacement from the box, what is the probability that the sum of the three numbers on the balls selected from the box will be odd?
　　A. 1/4
　　B. 3/8
　　C. 1/2
　　D. 5/8
　　E. 3/4
　　答案：C
　　解析：本题因为奇数和偶数个数相同，和也只有两种方式，所以三个数的和为奇数的可能性为 1/2。也可以考虑从这 100 个数中任取三个数的奇偶，可能性为：奇奇奇，奇偶偶，奇奇偶和偶偶偶，其中奇奇奇和奇偶偶两种情况的和为奇数，所以也得到可能性为 1/2
　　2. There are 1200 respondents to a poll, each favoring their preference for candidates A,B, and C. 54% favored A, 48% favored B, and 42% favored C, and there is 30% favored both A and B. What ’ s the largest possible number of respondents favoring C, but not C&B, nor C&A?
　　A. 25%
　　B. 30%
　　C. 28%
　　D. 38%
　　E. 40%
　　解析：A 和 B 的并集为：54% 48%-30%=72%，所 C 为 28%
　　 3. In an insurance company, each policy has a paper record and an electric record. For those policies having incorrect paper record, 60% also having incorrect electric record; For policies having incorrect electric record, 75% also having incorrect paper record.3% of all policies have both incorrect paper and incorrect electric records. If we randomly pick out one policy, what ’ s the probability that the one having both correct paper and correct electric records?A. 0.80
　　B. 0.94
　　C. 0.75
　　D. 0.88
　　E. 0.92
　　答案：B
　　解析：设总数为 x，设 incorrect paper record 有 y, incorrect electric record 有 z，则：
　　x · y · 60%=3% · x y=5%
　　x · z · 75%=3% · x z=4%
　　则，两者至少有一个错误的百分比为 5% 4%-3%=6%，所正确答案为 94%

　　4. If Bob can do a job in 20 days and Jane can do the job in 30 days, they work together to do this job and in this period, Bob stop work for 2.5 days and Jane stop work for x days, and the job be finished for 14 days, what is x?
　　A. 1.6
　　B. 3.2
　　C. 1.5
　　D. 1.25
　　E. 1.15
　　答案：D
　　解析：1/20 ( 14-2.5 ) 1/30 ( 14-x ) =1，得出 x=1.25
　　 5. The probability of A is 60% and the probability of B is 50%, what is the most possible probability that neither A nor B would happen?B. 0.40
　　D. 0.55
　　E. 0.68
　　解析：划出图表来可以一目了然：A， B 均不发生的大概率为 40%，小概率为 0. 因此选 B