GRE数学易错题范例解析

　　1 the sum of two numbers, x and y, equals twice their products. if x=3, what is the value of y?

　　这道题没大看懂?请问大家是这样么?x+y=2

　　x+y=2xy,求y.

　　2 if x is an integer and x237,what is the greatest possible value of x minus the least possible value of x?

　　我觉得这道题x的最大值为6,最小值为0,所以选6.

　　a.5 b.6 c.10 d.12 e.36

　　选D，最大为6，最小为-6.

　　3 三角形ABC，角B=X度，X90 度，比较三角形的周长与3倍AC的长度的大小，答案是B

　　AC是最大边,所以AB+BC+AC

　　2.0

　　比较the greatest value of p与1/2的大小，答案是C

　　答案错了,选B p+=2p^1/2 ==1/4 1/2

　　4 for the line with equation y=ax+b,the x-intercept os twice the y-intercept

　　比较the slope of the line 与1/2的大小，答案是D，但算出来是-1/2呀

　　还有截距为零的情况,所以D.

　　5 a certain moneymarket account that had a balance of $48000 during all of last monthearned $360 in interest for the month. at what simple annual interestrate did the account earn interest last month?

　　答案是9%,题目没看懂

　　意思是一个货币市场上个月共结余48000，用它赚了360的利息，问以年单利计算每年利率是多少?

　　36012/48000=9%

　　6 Of the positive integers that are multiples of 30 and are less than or equal to 360,what fraction are multiples of 12?

　　a.1/6 b.1/5 c.1/3 d.2/5 e.1/2

　　首先这道题我是对multilples of ....不大明白,这是什么意思啊?其次这道题怎么解呢?

　　在小于360的30的公倍数中,也是12的公倍数的占多少?30N360, 得N12,所以共有12个数满足题干.

　　又12与30的最小公倍数为60,其实此题是求是60的倍数又小于等于360所占比例,同理求出为6

　　所以,6/12=答案E

　　7 A certain teacher has a total ofat least 110 students enrolled in her classes.if the teachers has anaverage of exactly 27 students enrolled per class.what is the least possible number of classes that the teacher couldhave?

　　a.3 b.4 c.5 d.6 e.7

　　我觉得这道题就是用110除以27就好了,可是答案是选c的

　　是呀，110/27=4.04,如果是4个班，那么总人数为108，还剩2个。当然是5个班了。

　　8 a delivery service charges $0.02 per ounce for the first 16 ounces ofa shipment and $0.15 for each additional ounce of theshipment,

　　the delivery charges for x shipments weighing a combimed total of the pounds vs 567.00

　　这道题答案选的是D,不明白怎么会无法确定呢?我是这样算的:160.2+0.15...这样对么?

　　因为x是个未知数，所以你无法确定它的值。