[1006G]xiaoyaozi5566的GRE数学解题站

susuyaaUID: 2324593

17. If the number of microbes in a test tube increases by 25 percent per day, how many microbes are there in the test tube at the end of a given day if the number of microbes at the end of the next day is 240,000 ?
(A) 180,000
(B) 192,000
(C) 210,000
(D) 288,000
(E) 300,000

30. On a highway there is an electric pole every 96 feel. If the poles am numbered consecutively, what is the number of the pole 2 miles past pole number 56 ? (1 mile = 5,280 feet)
(A) 109
(B) 110
(C) 152
(D) 165
(E) 166

20. Three pumps, X, Y, and Z. removed water from a tank. Pump X removed 550 gallons, pump Y removed 1,250 gallons, and pump Z removed 1/3 of the total number of gallons removed by the three pumps combined. How many gallons of water did pump Z remove from the tank?
(A) 450
(B) 600
(C) 900
(D) 1,800
(E) 2,700

解答：
17、第二天的细菌数量是240,000，问前一天的细菌数量。用240,000除以125%就等于192,000了
30、每96feet有一个电线杆，而且电线杆的序号是连续的。从56号电线杆走2英里，一共有这么多电线杆：2*5280/96=110，因此电线杆的序号就为56+110=166
20、Z的工作量占1/3，说明X+Y共占2/3，因此Z是X+Y的一半，答案很显然了吧
by xiaoyaozi

susuyaaUID: 2324593

28. How many 3-digit integers, greater than 100. Are there in which the sum of the digits equals 3?
(A) Three
(B) Four
(C) Six
(D) Nine
(E) Twelve

210, 120,111,201,102,300 共6个,请问这种题只能一个一个代吗?



23. Approximately how many admissions were paid in 1940 ?
(A)300,000
(B)1,800,000
(C)3,000,000
(D)177,000,000
(E)3,000,000,000

谢谢了!!

解答：
28、这种题不用考虑第三个数，把问题变成前两个数之和不大于3，就是：10，11，12，20，21，30（因为第三个数自动在前两个数确定之后确定），这样是不是就容易多了？
23、用735除以0.24啊，然后注意单位是million，答案就是E了
by xiaoyaozi

jinziqiUID: 2387034

The amount by which the rescue squad's mortgage expenses exceeded expenses for utilities was what percent of expenses for utilities?
KEY: 200%
完全看不懂题。。o(╯□╰)o
顺便问问，就剩一礼拜了，看猴哥112中吗..还是应该看啥好。。
谢谢！

解答：
问题说的是rescue squad's mortgage expenses 超出expenses for utilities的部分占expenses for utilities 的比例是多少？如果没猜错的话rescue squad's mortgage expenses应该是expenses for utilities的三倍吧，因此超出部分占200%
那个猴哥112不知道，没用过，不过应该差不多的
by xiaoyaozi

susuyaaUID: 2324593

(9711)


22. For those industries that generated a total of

more than a million metric tons of waste in

1985, what was the approximate average

(arithmetic mean) total waste, in millions of

metric tons, generated per industry?
  
(A) 42

(B) 34

(C) 28

(D) 25

(E) 23

28. Which of the following numbers is NOT the sum

of three consecutive odd integers?

(A) 15

(B) 75

(C) 123

(D) 297

(E) 313

29. The price of product R is 20 percent higher than

the price of product S, which in turn is 30

percent higher than the price of product T. The

price of product R is what percent higher than

the price of product T?

(A) 60%
(B) 56%
(C) 50%
(D) 44%
(E) 25%

~谢谢!!

解答：
22、看黑线，超过100万吨的有四个产业，分别是2，6，50，100，加起来158，除以四就是39.5，最接近42了
28、三个连续的奇数之和是3的倍数（因为第一个和第三个相加等于第二个的两倍，加起来就是第二个的三倍），显然E
29、R=120%S,S=130%T，这个不用解释了吧
by xiaoyaozi

susuyaaUID: 2324593

(9804) 谢谢〜

19. A certain club is collecting money for a charity. A local company has agreed to contribute $ 1 to the charity for every $3 collected by the club. How much money must the club collect in order for the total amount for the charity, including the company contribution, to equal $24,000?
(A) $18,000
(B) $16,000
(C) $15,000
(D) $12,000
(E) $10,000

29. David and Michael charged Mr. Jimenez $3,000 to remodel his basement. To complete the project, David worked 4 days alone, Michael worked 1 day alone, and they worked 10 days together. If they each received the same amount of money for each day that they worked, how much of the $3,000 did David receive?

(A) $1,800
(B) $1,750
(C) $1,680
(D) $1,575
(E) $1,200

18. Of the 500 delegates attending a convention, 200 are Republicans and the rest are Democrats. One hundred of the delegates are vegetarians and, of those who are not vegetarians, 270 are Democrats. How many of the vegetarian delegates are Republicans?

(A) 30
(B) 40
(C) 50
(D) 60   
(E) 70


解答：
19、那个公司在club每筹集到3美元时就捐一美元，也就是说club筹集占3份，公司捐赠占1份，一共4份。如果要筹集24，000的话，那么club就应该筹集它的3/4，即为18，000
29、D工作了14天，M工作了11天，一共25天，3000美元来分。这样每天就是3000/25=120.D得到的钱就是120*14=1680
18、100个vegetarian，因此有400个非vegetarian，其中的270个是DEMO，因此130个是REPUB。而REPUB总共有200人，因此另外的那70人就是属于vegetarian了。故选E
by xiaoyaozi

susuyaaUID: 2324593

30. Which of the following CANNOT be expressed as the product of exactly 2 consecutive integers?
(A) (2) (3) (7)
(B) (2) (3) (7) (11)
(C) (2) (5^2) (13)
(D) (2^2) (3) (5) (7)
(E) (3^2) (11) (13)

解答
product指的是乘积，问的是哪一个不能表示成两个连续整数的乘积
A，6*7
B，22*23
C，25*26
D，20*21
E，no
by xiaoyaozi

susuyaaUID: 2324593

27. A certain doctor suggests that an individual’s daily water intake be 1/2ounce per pound of body weight plus 8 ounces for every 25 pounds by which the individual exceeds his or her ideal weight. If this doctor suggests a daily water intake of 136 ounces for a particular 240-pound individual, how many pounds above his or her ideal weight is that individual?
(A) 12(1/2)
(B) 16
(C) 30
(D) 50
(E) 120


25. If the total number of commuters to County W is twice the number to County Z, and if the average number of vehicles that transport commuters daily to County W is 30,000, what is the approximate average number of vehicles that transport commuters daily to County Z?
(A) 12,000
(B) 15,000
(C) 18,000
(D) 27,000
(E) 36,000

30. For a certain farm, soybean production increased by 25 percent from year X to year Y, and the selling price of soybeans decreased by 25 percent from year X to year Y. If the entire soybean production was sold each year, approximately what was the percent change in the revenues from the sale of the soybeans from year X to year Y?
(A) 56% decrease
(B) 6% decrease
(C) No change
(D) 6% increase
(E) 56% increase

题目太长就不知所云...冏
辛苦了〜感谢！

解答：
27、设这个人的ideal weight 为x，则有方程0.5*240+（240-x）*8/25=136，解得x=190，超过标准50磅
25、左图说的是：比如county W，是说平均1.2个人占用一个vehicle，因此去W用了30,000vehicle，去W的人数就是36000；而去Z的是它的一半，也就是18000，去Z的平均1.5人占用一个vehicle，用18000/1.5=12000
30、产量变为125%，售价变为75%，因此收入变为125%*75%=93.75%，降低了6%左右
by xiaoyaozi

尾羽UID: 2482591

The sum of n different positive integers is less than 100. What is the greatest possible value of n?
answer:13
这题看得懂，不会解，谢谢！

mokpoUID: 2408505

The sum of n different positive integers is less than 100. What is the greatest possible value of n?
answer:13
这题看得懂，不会解，谢谢！
尾羽 发表于 2009-10-19 13:54

要数最多，那么这些数要尽量小
1，2，3，4，5，6，7，8，9，10，11，12，13
和正好91<100
满足条件

尾羽UID: 2482591

要数最多，那么这些数要尽量小
1，2，3，4，5，6，7，8，9，10，11，12，13
和正好91
mokpo 发表于 2009-10-19 14:03

在考场上，我要从1一直加，加到13么？

xiaoyaozi5566UID: 2510336

56# 尾羽
肯定是从1开始加，这点是没有疑问的。
从1到n，和是n(n+1)/2，用这个公式，大概估计一下，就能找到你要的值了

susuyaaUID: 2324593

(9904) 谢谢~


30. Workers at Companies X and Y are paid the same base hourly rate. Workers at company X are paid 1.5 times the base hourly rate for each hour worked per week in excess of the first 37, while workers at Company Y are paid 1.5 times the base hourly rate for each hour worked per week in excess of the first 40. In a given week, how many hours must a Company X worker work in order to receive the same pay as a company Y worker who works 46 hours?
(A) 46
(B) 45
(C) 44
(D) 43
(E) 42


28. A developer has land that has x feet of lake frontage. The land is to be subdivided into lots, each of which is to have either 80 feet or 100 feet of lake frontage. If 1/9of the lots are to have 80 feet of frontage each and the remaining 40 lots are to have 100 feet of frontage each, what is the value of x?
(A) 400
(B) 3,200
(C) 3,700
(D) 4,400
(E) 4,760



A solid cubical block of wood has dimensions as
shown in the figure, and the block is to be cut in
half as indicated by the shaded region.

14. The total surface area  of one of the resulting halves of the block     36 square feet

Ans:A  


解答：
30、假设base rate是k，Y worker工作46个小时的工资是40k+6*1.5k=49k，再设X需工作z小时，那么37k+（z-37）*1.5k=49k，z等于45
28、除开前面的1/9，remaining 40 lots 则是占了8/9，因此总的lots数就是45个，总的x=5*80+40*100=4400
14、左边表示的是切开后的两半每一半的面积，两个9square feet的方形，两个4.5 square feet的三角形，一个阴影区域（9*根号2），加起来是27+9根号2>36
by xiaoyaozi

susuyaaUID: 2324593

a
b
ab

The lengths of the line segments are a, b, and ab, respectively. The line segments are drawn to scale.

15.   a                          1
Ans: A  (这题目看不懂??)


19. What percent of the integers between 200 and 999, inclusive, end with the digits “03”?
(A) 1%
(B) 25
(C) 3%
(D) 4%
(E) 5%

这题我的想法是:
百位: 2~9 , 所以8种选择
十位: 0~9 , 所以10种选择
个位: 3, 所以1种选择
(8*10*1)/(999-200)=0.1=10%  
不知哪里解错了??


30. What is the least integer value of n such that 1/(2^n)<0.001?
(A) 10
(B) 11
(C) 500
(D) 501
(E) there is no such least value.

解答：
15、ab比b长，所以a大于1
19、03...是指203，303，403这些数，一共有8个
30、2^10=1024（这个可要记住），因此正好比左边的小
by xiaoyaozi

susuyaaUID: 2324593

Carol’s age, in years, can be expressed by reversing the digits in her father’s age, in years. The sum of the digits in each age is 10.

10. The positive difference between Carol’s age, in years, and her father’s age, in years            36

Ans: B

之前好像有人讨论过这题, 所以答案是D吗?? 非常感谢

解答：
年龄的数字加起来是10，无外乎这么几种情况91，19；82，28；73，37；64，46；55，55；
看可能的情况：73，37；64，46
前面一个事36岁生的，后面一个事18岁生的
应该是D吧
by xiaoyaozi

尾羽UID: 2482591

Of the positive integers that are multiples of 30 and are less than or equal to 360, what fraction are multiples of 12?
answer:1/3


S is the sum of three consecutive integers, the greatest of which is x. In terms of S, which of the following is the sum of thress consecutive integers, the least of which is x?
A.S-6       B.S-3        C.S+3         D.S+6         E.2S
answer:D

THX a lot!

解答：
1、小于360的30的倍数有30，60，90，...，360，一共12个，其中又是12的倍数的是60，120，180，240，300，360，应该是1/2呀
2、S=(x-2)+(x-1)+x，而要求的那个东西=x+(x+1)+(x+2),因此就是S+6了
by xiayaozi