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标题: [求助]GWD-2-35 [打印本页]

作者: fhhrewr    时间: 2005-1-19 17:30     标题: [求助]GWD-2-35

先谢谢了

Q35:

p is an integer; n is an integer; and p/n is an integer. Is p/n odd?

(1) p is divisible by 4.

(2) n is divisible by 4.

A. Statement (1) ALONE is sufficient, but statement (2) alone is not sufficient.

B. Statement (2) ALONE is sufficient, but statement (1) alone is not sufficient.

C. BOTH statements TOGETHER are sufficient, but NEITHER statement ALONE is sufficient.

D. EACH statement ALONE is sufficient.

E. Statements (1) and (2) TOGETHER are NOT sufficient.

[此贴子已经被作者于2005-1-19 17:34:13编辑过]


作者: sammen    时间: 2005-1-19 21:32

没有思路,我选E


作者: mikejia    时间: 2005-1-19 21:40

1). suppose p=4K, 4K/n=integer if the result is odd, premise is n odd, condition 1 is not enough;

2) Suppose n=4m, if k/4m=odd => k must odd. condition 2 is not enough too

both 1) and 2) together p is even, n is even => p/n=4k/4m=k/m, k and m can be odd or even. so both are not enough.

my choice is E too.

please kindly give some advices.


作者: robert    时间: 2005-1-20 09:59

这道题选E

向这种is的题当无法确定时,只需列出反例即可。

比如由1我们假设p=8 n=2 则8/2=4 而 p=12 n=4 则12/4=3

同理由2也无法确定是否为odd

1+2,我们假设p=4,n=4 则p/n=1 而p=8,n=4则p/n=2

所以E


作者: fhhrewr    时间: 2005-1-20 10:48

谢谢,这种题型比较怪。那么比较通用的解题方法就是举反例啦?


作者: mikejia    时间: 2005-1-20 12:18

我的不通用吗?

不过反例更快更准确。


作者: robert    时间: 2005-1-20 12:59

反例是一种方法,

反证法就是一种通用的方法


作者: sammen    时间: 2005-1-20 22:25

呵呵,俺也是找的反例,这样可能快点。
作者: sammen    时间: 2005-1-21 16:41

真是真理,只要对,管她什么方法不方法的.






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