[原创]8月数学机经全总结（讨论稿，8.23，198题）

atongmu

以下是引用joywzy在2003-8-23 17:18:00的发言：

atongmu，你是不是做错了？

应该是。[1.5(60-50)+125*0.08]/(50*1.5+125)，问的是increase percent

我笔误了，答案没错。

zjxmlily

189. there are 500 marbles in a jar. 200 are red, 100 are blue, and 200 are green. if two marbles, one at a time without placements, are taken from the jar. what’s the possibility that both marbles are red?

请问without placements是指不考虑两个的顺序吗？

joywzy

T166，A，只能=15。

atongmu

以下是引用zjxmlily在2003-8-23 17:29:00的发言：
189. there are 500 marbles in a jar. 200 are red, 100 are blue, and 200 are green. if two marbles, one at a time without placements, are taken from the jar. what’s the possibility that both marbles are red?
  
请问without placements是指不考虑两个的顺序吗？

所有红球都同质。

monicar

181. 某城市人口中在职的为64%，48%是男性在职，问在所有在职职工中女性占多少？
参考答案：（25%）

好象题目不全吧.

   


183. car a can go 25 miles/gallon of gasoline, while car b can go 11.9 miles/gallon of gasoline. if both cars are driven 12,000 miles, how many more gallons of gasoline will car b consume than will car a? (rounded to the unit digit)

12000/11.9-12000/25=1084-480=604

184. a company increases its costs/labor charges from $50/hour to $60/hour and enhances its parts charges by 8%. a certain job requires 1.5 hours of labor charges and parts charges, and the parts charges before change were $125/hour. what percent will the total charges for this job increase?

1-(1.5*60+125)/(1.5*60+125*1.08)=1/9

185. among the 600 attendees of a conference, 250 are republicans and 100 vegetarians. how many of the republicans are vegetarians?
1) 300 are neither republicans nor vegetarians
2) 200 republicans are not vegetarians

D

186. the average salary for company a is $3500, and the average salary for company b is $4500. how many people are in company a?
1) the average salary for company a and company b is $4200
2) there are totally 500 employees in a and b.

C

187. ax+by+c=0. the slope is 1/2. what’s the value of b?
1) a=2;
2) c=4
A.

188. 30!/10! is expressed as the product of integers. the biggest integer is 30. what’s the smallest integer?
参考答案：
1 . if it is the product of consecutive integers, the answer is 11.

189. there are 500 marbles in a jar. 200 are red, 100 are blue, and 200 are green. if two marbles, one at a time without placements, are taken from the jar. what’s the possibility that both marbles are red?
C200,2/c500,2

N整数，N是否是平方数？
（1）4N是平方数
（2）N^3是平方数
参考答案：
D

190. 123456789的平方，unit is the X, tenth is the Y, ask X=? Y=?
参考答案：
思路：X=1, y=2

191. 直角三角形，一边为５，斜边为10，５所对的角和5，10夹角的补角的关系。
参考答案：
   4:1

192. 一学校，　老师：学生＝１：１３，　今年老师多了１４，　学生多了７４，　比例变为１：１２，　ask: this year the number of the students.(数不准）
参考答案：
1222

193. 一人，　工资由３２，０００增加到３３，０００。问增长比例。
参考答案：
思路：
1000/32000=1/32
194. １、２、３、５和另一数A,A 是１，３，５中一个，问Ａ是哪个能使Ａ加入四个数后的median=average.
参考答案：
没有答案


196. Ｘ，Ｙ为interger,X=?
2X+4Y=10
XY<0(不准）
参考答案：
思路：1不行，2不行，1+2还不行，E。

197. 75miles, 去 35m/h,回45m/h,ask the total time
参考答案：
思路：75/35+75/45

198. 一个酒吧的收费标准:10人以内收120元,10人到20人收80元加每人4元,20人以上每人收8元.C,D两组人去酒吧,问C组人有多少?
条件一:C组人比D组人多3人
条件二:C组人比D组人多交4元
参考答案：c
思路：显然A、B不对。而且显然C组人和D组人不在同一个收费区，因为Sc>Sd，所以，有两种情况：
1、C在I区，D在II区，而且Sc>=7，
如果Sc=7, then Sd=10，则Pc=120, Pd=80+10*4=120，不符合;
如果Sc=8, then Sd=11，则Pc=120, Pd=80+11*4=124，符合;
如果Sc=9, then Sd=12，则Pc=120, Pd=80+12*4=128，不符合;
2、C在II区，D在III区，而且Sc>=18
如果Sc=18, then Sd=21，则Pc=80+18*4=152, Pd=8*21=168, 不符合;
如果Sc=19, then Sd=22，则Pc=80+19*4=156, Pd=8*22=176, 不符合;
如果Sc=20, then Sd=23，则Pc=80+20*4=160, Pd=8*23=184, 不符合;
所以选C。复杂

joywzy

monicar,只要说与答案不一样的，一样的就不用说了吧。

zjxmlily

39. t1.t2，....,tn；tn+1=tn/2，问t5=?
(1) t3=1/4
(2) tn-t1=15/16
参考答案：C
思路：

我觉得是A，因为有（1）可以推出t1，再加上题目已经给出了q=1/2,应该可以求出t5了吧，而（2）无法知道n所以推不出，这是个等比数列吧

zjxmlily

67. 某人有bookcase, arrange 10 books per shelf and no books left. If he acquired 10 additional books, and arrange 12 books per shelf, no books left. Ask how many books he has before acquiring the addition 10 books
A before acquiring, his books less than 96
B before acquiring, his books more than 24
参考答案：a
思路：

这题能不能讲解一下，不太理解啊？谢谢

zjxmlily

70. original selling price=加上x% 后的retail price, and final sale price=y倍的original selling price, Ask final price?
A xy的值
B 3x+4Y的值  
参考答案：A
思路：

这题怎么求呢？

zjxmlily

102. 说财产tax是compound tax 的百分几, compound tax 由 custumor (?) tax  和 school tax 和另外一个tax 分别取 5:4:11 (数值5,4位置不确切)问财产tax
1: 给出school tax是多少
2: 给出另外1个tax的直,具体是什么直我不太记得了
参考答案：估计是E,除非2说的是compound tax
思路：

我也觉得这道题选D啊，知道了任何一个tax不是可以根据比例推出compound tax，进而推出财产tax吗？