十个新GRE数学易错题解析和GRE和GMAT数学常考数学公式介绍 GRE和GMAT数学常考数学公式介绍 为大家总结了一些GRE和GMAT数学常考数学公式,希望对各位考生有用。GRE和GMAT数学考试难度不大,但是需要各位考生将一些常考数学公式进行熟知了解。 (a+b)(a-b)=a2-b2 (a+b)2=a2+2ab+b2 (a-b)2=a2-2ab+b2 (a+b)3=a3+3a2b+3ab2+b3 (a-b)3=a3-3a2b+3ab2-b3 一元二次方程ax2+bx+c=0的解x?,?=(-b±√b2-4ac)/2a *Simple Interest:利息Interest=本金Principal?时间Time?利率Rate。 *Compound Interest:A=(1+R)n;A为本利和,P为本金,R为利率,n为期数。 *Discount=Cost?Rate of Discount *Distance=Speed?Time *Pythagorean Theorem(勾股定理):直角三角形(right triangle)两直角边(legs)的平方和等于斜边 (hypotenuse)的平方。 *多变形的内角和:(n-2)×180°,总对角线数为n(n-3)/2条,从每一个顶点引出的对角线数为(n-3)条;式中:n为多边形的边数 *平面直角坐标系中,A(x1,y1)和B(x2,y2)是任意两点,C(x,y)是线段AB的中点,则x=(x1+x2)/2,,y=(y1+y2)/2 *平面图形的周长和面积: 十个新GRE数学易错题解析 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) x+y=2xy,求y. 2 if x is an integer and x2(x的平方)<37,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,X>90 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(1-p)与1/2的大小,答案是C 答案错了,选B p+(1-p)>=2p(1-p)^1/2 => p(1-p)<=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? 360*12/48000=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?30N≤360, 得N≤12,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 (arithmetic mean) 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,(1pound=16ounce) 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:16×0.2+(25*16-16)×0.15...这样对么? 因为x是个未知数,所以你无法确定它的值。 9 the cost per gram of carrots if 3 cans of carrots cost $0.90 the costper gram of onions if 5 cans of onions cost $1.50 无法确定,没有告诉1can有多少克? 10 X is an integer, and the remainder when 2X is divided by 4 is 0. The remainder when X is divided by 4 0 选D,当x=2,-2时,余数为2,-2,其它情况为0 |
新东方GRE网络课堂>>
新东方GRE