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PREP MATH 请求答疑贴

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楼主
发表于 2009-5-14 11:24:00 | 只看该作者

PREP MATH 请求答疑贴

1.

For every positive even integer n, the function h(n) is defined to be the product of all the even integers from 2 to n,inclusive. If p is the smallest prime factor of h(100)+1, then p is

-Between 2 and 10

-Between 10 and 20

-Between 20 and 30

-Between 30 and 40

-Greater than 40

2.

According to the directions on a can of frozen orange juice concentrate,1 can of concentrate is to be mixed with 3 cans of water to make orange juice. How many 12-ounce cans of the concentrate are required to prepare 200 6-ounce serving of orange juice?

- 25

- 34

- 50

- 67

- 100

3.

If each term in the sum a1+ a2+ …….an is either 7 or 77 and the sum equals 350, which of the following could be equal to n?

- 38

- 39

- 40

- 41

- 42
   

4.

For which of the following functions is f(a+b)=f(a)+f(b)for all positive numbers a and b?

-          f(x)=x^2

-          f(x)=x+1

-          f(x)=x

-          f(x)=2/x

-     f(x)= -3x

5.

A certain library assesses fines for overdue books as follows. On the first day that a book is overdue, the total fine is $0.10. for each additional day that the book is overdue, the total fine is either increased by $0.30 or doubled, whichever results in the lesser amount. What is the total fine for a book on the fourth day it is overdue?

- $0.60

- $0.70

- $0.80

- $0.90

- $1.00

6.

of the students who eat in a certain cafeteria, each student either likes or dislikes lima beans and each student either likes or dislikes Brussels sprouts. Of these students, 2/3 dislike lima beans; and of those who dislike lima beans, 3/5 also dislike Brussels sprouts. How many of the students like Brussels sprouts but dislike lima beans?

(1)       120 students eat in the cafeteria

(2)       40 of the students like lima beans

KEY

7.

in the rectangular coordinate system, are the points(r,s) and (u,v)equidistant from the origin?

(1)   r+s=1

(2)   u=1-r and v=1-s

KEY:C

8.
In the figures above, if the area of the triangle on the right is twice the area of the triangle on the left, then in term of s, S=2s
两个三角形,左边的底边为s 右边的底边为S,他们的内角都相等
没想通?

9.
In May Mrs.Lee’s earnings were 60% of the Lee family’s total income. In June Mrs.Lee earned 20% more than in May. If the rest of the family’s income was the same both months, then, in June, Mrs.Lee’s earnings were approximately what percent of the Lee family’s total income?

-          64%
-          68%
-          72%
-          76%
-          80%

怎么算都是72%

10.
Store S sold a total of 90 copies of a certain book during the seven days of last week, and it sold different numbers of copies on any two of the days. If for the seven days store S sold the greatest number of copies on Saturday and the second greatest number of copies on Friday, did Store S sell more that 11 copies on Friday? (1)   Last week Store S sold 8 copies of the book on Thursday.

(2)   Last week Store S sold 38 copies of the book on Saturday.

11.

Is the integer n odd?

(1)   n is divisible by 3

(2)   2n is divisible by twice as many positive integers as n

KEY: B

12.

Working alone at its own constant rate, a machie seals k cartons in 8 hours, and working alone at its own constant rate, a second machine seals k cartons in 4 hours. If the two machine, each working at its own constant rate and for the same period of time, together sealed a certain of cartons, what percent of the cartons were sealed by the machine working at the faster rate?

 -          25%
 
-          (33*1/3)%
 
-          50%
 
-          (66*2/3)%
 
-          75%


请好心人能给与解答,呵呵,
                


[此贴子已经被作者于2009-5-14 11:54:43编辑过]
沙发
发表于 2009-5-14 12:03:00 | 只看该作者

大哥 你也真实诚,一下贴这么多,本来想帮忙也吓着了,建议下一个prep数学精解 看不懂再把个别题拿来大家探讨比较好  

板凳
发表于 2009-5-14 12:27:00 | 只看该作者
(1) 2~100 的even numbers = 2550.   2550+1= 2551  -> prime number

(2)200 * 6 =1200 ounce.

    

1200 / 4 = 300 (sets for concentrate unit)


    300/12 = 25 (cans)

(3)350 = 7 * 50 = 77 + 63 + 210

    

77 (1), 63 (9), 210 (30) => n=40

(4) 你帶 2, 5 進去做  就知道 只有乘法會ㄧ致

(5) 0.1 + 0.3+0.3   是每一天結束才算過期  所以周4沒有罰錢

先吃飯去~


地板
发表于 2009-5-14 13:35:00 | 只看该作者

好多题...

1)如题h(100)+1=(2*4*5*...*100)+1=2^50*(1*2*3*...*50)+1

因此,1 2 3...50均不是其最小质数,因此选择大于40

2) 3) 4) 同楼上~

5)可以看做阅读题做...不过我和楼上有点不同看法关于这句话的理解:the total fine is either increased by $0.30 or doubled, whichever results in the lesser amount.

我认为第一天0.1之后有两种选择(A)increased by $0.3 (B)doubled

因此第二天0.1*2=0.2;第三天0.2*2=0.4;第四天因为0.4+0.3<0.4*2因此选择前者,第四天为0.7

6)算不出D,等NN吧~

7)点(A,B)到原点距离就是根号下(A^2+B^2),代数答案显然。

8)如题两三角形相等,左边面积比右边面积是1:2,那么左边底边s比右边底边S就是1:根号2,化简得到答案。

9)设May total income为X,如题May Mrs.L赚到60%X,其余收入为40%;June Mrs.L赚到60%X*120%,其余依然为40%。

因此答案为(60%X*120%)/(60%X*120%+40%X)=64%

10)我只算到E,等NN~

11)条件1不一定,比如6;条件2确定,可举例。 
n=21
它的因子为 1,3,7,21,总共4个
2n的因子为 1,2,3,6,7,14,21,42,总共8个

n=6
它的因子为 1,2,3,6,总共4个
2n的因子为 1,2,3,4,6,12,总共6个
        

12)慢的效率为k/8,快的效率为k/4,一起工作为(k/4)/(k/4+k/8)=2/3

做了好久JJ正好拿英文题目练练手嘿嘿~

不过还是找有精解的PP做比较好哦,因为那些精解会更权威更详细的~

5#
 楼主| 发表于 2009-5-14 14:53:00 | 只看该作者

多谢

我做了100多道,碰到了这么12个不晓得怎么搞,谢谢h5641 和 WarlockNini,你们真的好厉害。

6#
发表于 2009-5-14 15:46:00 | 只看该作者

第10题  由(2)  星期六卖了38本  那么剩下六天公卖52本

设星期五卖了11本  那么剩下五天最多卖(6+7+8+9+10)=40本,因为星期五是第二多的 而且每天都不同。加起来只有89本 

所以星期五卖了多余11本  (1)不充分  选b

7#
发表于 2009-5-14 15:55:00 | 只看该作者

还是没看懂第一题怎么解

6)120*1/3=40 所以(1)和(2)是等价的

 like Brussels sprouts but dislike lima 和dislike lima and like Brussels sprouts 是一致的,120*2/3*2/5即可

 

8#
发表于 2009-5-14 16:15:00 | 只看该作者

 呃?

     均余1?


[此贴子已经被作者于2009-5-14 16:17:22编辑过]
9#
发表于 2009-5-14 16:55:00 | 只看该作者
第三题,穷举,77最多可以有0、1、2、3、4项,求出每种情况下剩下的7的项数
第六题,实际就是求only dislike lb的人数,即是总人数的2/3-2/3*3/5-(1)充分或者2/3的2/5-(2)充分
10#
发表于 2009-5-14 18:05:00 | 只看该作者
第11题 (2),假定n有k个因子,
n是奇数时,2n必有(1+1)*k个因子,是2倍关系
n是偶数时,n=2的j次方*剩余的素数表达(j>=1),因子从(j+1)k增加到(j+2)k,因为j>=1,一定不是2倍关系
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