295. A triangle is on the xy plane, with coordinates A, B, and C. B and C coordinates are given on the plane. What is the coordinate of A? 1) AB=x 2) BC=y (x and y are given as numbers, but I forgot them all!!) (Just try to image or learn the concept)
from 1) A点在以B为圆心x为半径的圆上 无法确定哪个点 not A
from 2) 只能求出BC的长度, 无法确定A点 not B
union: 不能确定A点 so E
没看懂题目
296. Is n a prime number? 1) n is a factor of 125 2) n is a factor of 75
遇到这种题 直接选E, 如果你能通过任何条件能判定一个数是不是素数, 你就能证明1 + 1 = 2 了
297. 3x-4y>0, is x>y? 1) x= 1 2) y=2 : (數字不確定)
3x – 4y > 0 x > 4/3y
from 1) x > y + 1/3y, x – y > 1/3y, when y > 0 x – y > 0; when y < 0 x = 1 > 0 > y
from 2) 属于1) 中 y > 0的情况
so D
298. (1/8)^2 (这题用分数算, 答案全是分数的形态): Answer(0.25)^3
这不就是 1/8 * 1/8 = 1/64 淡定。。。。
299. Given a rectangle, with sides PQRS. The area is 4根号3, PR is twice of PQ (PR是对角,斜边). What is PR?
xy = 4(根号3)
2x = 根号(x^2 + y^2) x = 2 PR = 4
291. If n is an integer between 10 and 99 and n is divisible by 7, the remainder is 3, is n< 80?
1) When n is divided by 5, the remainder is 0
2) When n is divisible by 3, the reminder is 0
Inclusive ?
n = 7m + 3
from 1) n = 5k n = 35t + 10, t = 0, 1, 2, 3, … so not A
from 2) n = 3s n = 21a + 24 a = 0, 1, 2, 3, …so not B
union n = 35t + 10 , n = 3s n = 105 k + 45 在 10 到 99 只有45满足条件 so C
两个通式没看懂?
292. If y = [4(n+1)-5]/[(n+1)(n+2)], which of the following has the greatest value?
A. -1/y
B. (1/y)2
C. y2
D. (1/2y)
E. y
当 n = 0 时 y = 1/2 代入 得 B
A吧?
293. If a store sells three kinds of belts and each account for(占有..百分比)20 percent, 50 percent, and 30percent of the revenues respectively(分别), what is the average price for each belt sold?
Price of each belt is $5, $3, and $10 respectively
5,3,10, 分别卖了a, b, c条, 总收入为 revenue
5 * a = 0.2 revenue
3 * b = 0.5 revenue
10 * c = 0.3 revenue
所求 = revenue / ( a + b + c) = 30 revenue / ( 30 a + 30 b + 30 c)
= 30 / ( 6*0.2 + 10 * 0.5 + 3 * 0.3)
= 30 / 7.1
revenue / ( a + b + c)=1 /(0.2/5+0.5/3+0.3/10)
294. A museum has 40 exhibits, total of 2000 visits last month. What is the average revenue for each exhibit?
1) Revenue from each child ticket and adult ticket sold are $8 and $12 respectively
2) More than half of the exhibit account for revenue of $2000
average revenue for each exhibit revenue / 40 revenue ?
from 1) x + y = 2000, 8x + 12y 无法求出 not A
from 2) revenue 无法求出
union: 8x + 12y > 2000 无法求出 revenue so E
286. If 2.164 *1017– 5.12*1016 = 1.652 *10m , what is m?
这m是个负数,剩下的排除吧,就别算了,我是没有想到什么更好的办法,有人想到了, 告诉我一声,谢谢
287. If |2x-5| = x-3, how many solutions does x have?
4x^2 – 20x + 25 = x^2 – 6x + 9 3x^2 – 14x + 16 =0 △ < 0 no solutions at all
288. If Integer x=5^m + 3^n, what is x?
1) mn = 20
2) m+n = 9
x = ? x = 5^m + 3^n m, n
from 1) mn = 20 can not get m, n so not A
from 2) cannot get m, n so not B
union: n = 4 m = 5 or n = 5 m = 4
E
289. If n=(x-3)/(y-4),what is n?
1) x=3
2) y=2
A
290. Machine x can complete a task in 8 hours and machine y can complete the same task in 4hours. How much of a task does x completes if x and y are working together?
x 每小时完成任务的 1/8; y 每小时完成任务的 1/4
x, y一起做,每小时完成任务的 1/8 + 1/4即 3/8其中 x占1/8
x做1/3
282. One questionstates that hundredth digit is more than three times of the tenths digits of an integer, which of the following MUST be true. (这题是说一个 数, 百分之一的数大于三倍的十分之一数, 下列选项哪个是对的.
同意
283. X is 20percent more than y which is 20 percent than z, w is 20 present less than x,how much greater than z is x. (答案选项是百分比的型式)
x = 1.2y; y = 1.2 z ; w = 0.8x x = 1.44z so 44%
给w是做什么的?
284. Is x > 5?
1) x2> 25 这里应该是 x^2 吧?
2)2x + 7 > 0 Answer: C
from a) x > 5 or x < -5 not A
from b) x > - 3.5 x > 5 or -3.5 < x < 5 not B
union x > 5 C
285. In a hospital, 40percent of the newborn are boys and 10 percent of them have weights greater than 3.18kg. And 10 percent of the newborn boys have weights greater than3.18kg. What percent of the newborn have weights greater than 3.18kg in the hospital?
1) 20 percent of the newborn girls have weights less than 3.18kg
2) 6percent of the total new born have weights greater than 3.18kg
题目中的红色部分有用吗?
60% of the newborn are girls from 1) 80% of the newborn girls have weights no less than 3.18kg we do not know what percent of newborn girls have weights equal to 3.18 kg. can not get what percent of newborn girls have weights greater than 3.18kg not A
from 2) 6% (什么意思? total new born 与 newborn 不一样吗?) B
272. (a-x)(b-x)-4h^2=0是否有两个解? (1)a≠b (2)h≠0
设 b = a + n 由条件1) n <> 0 ;
(x-a)(x-b) = (2h)^2 (x-a)(x –a -n) –(2h)^2 = 0 (x-a)^2 – n(x-a) – (2h)^2 = 0;
△= n^2 + 4 (2h)^2 > 0 有两解
from 2) △ > 0
so D
V2 第272题,选的D,JJ思路很好,幸亏看了,不然考试就傻了
273. xy^2=z^3 问z^3>0?
a. x^2y>0
b. xy<0 ? 记不清了
we should determine whether xy^2 > 0 .
form a) x^2y > 0 y > 0 but we cannot know whether x is great or less than 0 no A
from b) xy < 0 即x,y 异号 when x > 0 : xy^2 > 0, when x < 0 xy^2 < 0 not B
union: y > 0, x,y异号 x < 0 xy^2 < 0 z^3 < 0 C
276. 有一个三位数,知道个位是百位的2倍,这个数可以被3整除, 问可以得到那个是对的
a十位是非零的数
b十位是奇数
c十位是三的倍数
设 百,十,个位数分别是 a, b ,c
c = 2a, a + b + c = 3n 3a + b = 3n
a) 当 b = 3 时 3(a + 1) = 3n a) 不是必须的
b) 当 b = 6 时 3(a + 2) = 3n b) 不是必须的
c) 假设 b 不是三的倍数 设 b / 3 模 1, 即 b = 3m + 1 3a + 3m + 1
永不为可被3整除 c) 是必须的
268. P售价30元,Q售价20元,P售出的量是Q的两倍,还是Q是P的两倍记不清了,是twice as many A as it has B这种句子,求所有售出商品平均价
( 30 * P + 20 * Q ) / (P + Q), P = 2Q (30 * 2Q + 20 * Q) / 3Q 80 / 3
271. ︱x︱+x/2<4, x=? (1)x>-12 (2)x<-6
1) 0 < x < 8/3 or -8< x <= 0 not A
2) -8< x < -6 not B
union: -8 < x < -6 E
V2 DS,x是整数,|x|+x/2<4,问x=?
(1) x>-12
(2) x<-6
选B,因为由图像或者分类讨论得 -8<x<8/3 (1)条件不能给出结果,(2)条件可得x=-7,因为整数的条件。