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标题: Prep第一次,请大家帮忙分析(含错题求解) [打印本页]

作者: smallzhang    时间: 2007-11-8 06:34     标题: Prep第一次,请大家帮忙分析(含错题求解)

本月30日下午一点考试,还有9天,实际有效准备时间为8天。今天下午一点考的prep(作文没考,其他都是严格按真实考试执行,包括喝红牛,呵呵。)

结果:M49 V34 690

M:37错11,很奇怪能到49分,前十错2。

V: 40错17,(时间来不及,做到34时时间只有5分钟左右,结果最后乱点都没点完,最后8题错6个),错17个还能得34同样让我吃惊,不过前十也是错两个。具体分布为:SC 16错11,CR 10错3,RC 14 错3。SC一直头大,做了一遍OG(边做边分析了一遍后面的解释,看了LZM,BY,错题大部分看看也明白错在哪里,就是考试的时候时间紧,没有时间分析清楚就选了。)

---时间一次是个大问题,从两周前开始做GWD(一共做了7套XY13),一直都是超时25分钟的样子,今天做prep一直提醒自己加快,结果还是做不完,估计如果正常做完时超时10分钟左右。郁闷啊,不知怎么提高。难道真的只有猜?

最后谈谈M,之前做过GWD的一套题,错4个,而且时间剩余10分钟。但今天明显感觉时间不够用,难道PREP的数学比GWD难?

另外还有几个题目错了还是不明白,请教各位:

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,the P is:

1>2~10  2>10~20 3>20~30 4>30~40 5>greater than 40------The answer is 5>

2,For how many integers is 2的n次方=n的2次方(不会输次方,没法子)?

The answer is TWO---- 看到答案后算出应该是2和4,但是请问一下考试时有什么方法?还是简单代入?

3,if X>Y的2次方>Z的4次方,which of the following statements could be true?

1> x>y>z        2,  Z>Y>X   3 X>Z>Y

答案为1,2,3全对,非常奇怪,如果x=0.1 y=0.2 z=0.3 的话应该是满足题目要求,但是明显和答案不一致。

4,At least 100 students at a certain high school study Japanese.If 4 percent of the students at the school who study French also study Japanese,do more students at the school study French than Japanese?

1>16 students at the school study both French and Japanese.

2>10 percent of the students at the school who study Japanese also study French.

答案为B。

5 If the integer a and n are greater than 1 and the product of the first 8 positive integers is a multiple of a  的n次方,what's the value of a?

1> a的n次方=64

2》n=6

答案为B。

唉,数学居然还有这么多没搞清楚,晕啊。本来还想考700呢,不知道还有没有办法,各位大牛指导一下啊,多谢!


作者: linlin3151    时间: 2007-11-8 19:16

因为题目里面有实验题,不算分, 所以有错也可以拿满分, 模考和真考都有实验题。 祝你成功!

QUOTE:
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,the P is:

1>2~10  2>10~20 3>20~30 4>30~40 5>greater than 40------The answer is 5>

可知,n=2k, h(n) = (2)x(2x2)x(2x3)x ... x(2k) = (2^k)(k!)
所以,h(100)+1 = (2^50)(50!) + 1
-> h(100)+1 is 奇数, p is not 2
-> h(100) 含有 3 作为 factor, 因此 h(100) = 3y (y is integer); 然而, 3y+1 不能被 3 整除, 所以 h(100)+1 不含有 3 作为 factor
-> 同理, 所有小于50的质数都不能作为 h(100)+1 的 factor
-> 总结可得, p>50, 选 <5>

QUOTE:

2,For how many integers is 2的n次方=n的2次方


要列举,
-> 代入 0, -1, -2, 可很快确定 n > 0
-> 代入 1, 2, ... 从 n=5 开始, 2^n 已抛离 n^2

QUOTE:

3,if X>Y的2次方>Z的4次方,which of the following statements could be true?

1> x>y>z        2,  Z>Y>X   3 X>Z>Y

答案为1,2,3全对,非常奇怪,如果x=0.1 y=0.2 z=0.3 的话应该是满足题目要求,但是明显和答案不一致。


此题要求判断所给答案的正确与否,并不是要列出全部可能性

QUOTE:

4,At least 100 students at a certain high school study Japanese.If 4 percent of the students at the school who study French also study Japanese,do more students at the school study French than Japanese?

1>16 students at the school study both French and Japanese.

2>10 percent of the students at the school who study Japanese also study French.

答案为B。


从题目可知, J>=100, (4%)F = JF  (J - 读日人数, F - 读法人数, JF - 同时读日法人数)
从<1> 可推出 F=400; 但 J 不确定
从<2> JF = (10%) J = (4%) F; 所以 F > J
-> 选 B

QUOTE:

5 If the integer a and n are greater than 1 and the product of the first 8 positive integers is a multiple of a  的n次方,what's the value of a?

1> a的n次方=64

2》n=6

答案为B


从题目可知, 8! = k (a^n)  -> k is integer
<1>, a^n = 64, a 可以是 8, 或 4, 或 2
<2>, 因为 8! = (2^7)(3^2)(5)(7), 当 n=6 时, a 只能是 2
-> 选 B

作者: smallzhang    时间: 2007-11-9 06:07

多谢!牛人一个!

另:第三题有人说是:could be true说明只要有能满足的情况即可,不一定要在所有的情况下都满足,这样题目就很容易理解了。






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