lsat 1-6

Snazzy · 发表于 2003-12-19 00:05:00

6. No senator spoke at the convention unless he or she was a Democrat. No Democrat both spoke at the convention and was a senator.
Which one of the following conclusions can be correctly drawn from the statements above?
(A) No one but senators spoke at the convention.
(B) No Democrat spoke at the convention.
(C) Only Democrats spoke at the convention.
(D) No senator spoke at the convention.
(E) Some Democrat senators spoke at the convention.

Please do me a favour. Is there a quicker way to do these kinds of questions? It took me ten years to figure out the relationship of who is who. The more I worry bout the time, the less effective i become. The answer is D. Thanks

mindfree · 发表于 2003-12-19 01:04:00

Just wrote a lot and got deleted. So I will be short this time.

There are two things you need to do in CR: understanding and figuring out line of reasoning. The first is about knowing what each sentence or word means. The second is about knowing what connections are among those sentences or words.

I think you can easily understand the words and sentences. So the key here is the reasoning. And the key of that is the key word.

A unless B ==> A --> neg B. I will go unless you go ==> I will go --> you do not go (or you go --> I will not go).

Not A unless B ==> A --> B (or neg B --> neg A). Note that it is a bit different from above.

No ... both ==> either ... or... Democrat either spoke or was a senator.

Now you should put them together and figure out the connection among all the elements. The answer is pretty clear.

crusaders · 发表于 2003-12-19 01:53:00

i am mindfree nn' fans
Pls allow me to show something interesting

L1 No senator spoke at the convention unless he or she was Democrat.
-(Senator + spoke) =-Democrat
----->If a senator spoke at the convention, he or she must be a Democrat.
------>Senator + spoke = Democrat
L2 No Democrat both spoke at the convention and was a senator.
-(Democrat + spoke) =Senator
----->ALL Democrat spoke at the convention was not a senator.
----->Democrat + spoke= -Senator

推导
Senator + spoke =Democrat
Democrat + spoke =-Senator
-------------------------------------------------------
Senator +spoke +spoke = -Sentor
2Senator=-2spoke
spoke=-Senator
senator=not + spoke

A.Spoke=Senator
B.Spoke=-Democrat
(迷惑选项)C.Only Democrats spoke at the convention.
从仅有的以知条件中推不出Democrats=spoke来.
D.Spoke=-Senator(答案)
E.Democratsenator=Spoke(无关)

[此贴子已经被作者于2003-12-19 2:05:17编辑过]

Snazzy · 发表于 2003-12-19 13:19:00

thanks, guys, give me some time to think about it

tianwan · 发表于 2004-4-3 01:08:00

not A,unless B: A->B ；no A, unless B: A->B,

屡试不爽。

tianwan · 发表于 2004-4-3 01:13:00

以下是引用mindfree在2003-12-19 1:04:00的发言：
“A unless B ==> A --> neg B. I will go unless you go ==> I will go --> you do not go (or you go --> I will not go).”

可是feifei和陈向东都说：A unless B ==>neg A --> B。

tianwan · 发表于 2004-4-3 11:11:00

以下是引用mindfree在2003-12-19 1:04:00的发言：

No ... both ==> either ... or... Democrat either spoke or was a senator.

No democrat both spoke at the convention and was a senator.除了表示 democrat either spoke or was a senator，还应该包括 democrat neither spoke nor was a senator.

也就是说：democrat1: speak, not senator;democrat2: not speak, senator; democrat3: not speak, not senator.

我被否定表示法弄糊涂了，请NN指正，我的理解是不是对的？

[此贴子已经被作者于2004-4-3 11:26:18编辑过]

tianwan · 发表于 2004-4-3 14:01:00

up！请NN回答啊。

yezi-chen · 发表于 2004-11-7 02:46:00

看了nn的解释我是这么理解的：

No senator spoke at the convention unless he or she was a Democrat 推出只有d且senator的人才speak

No Democrat both spoke at the convention and was a senator.推出 1）D speak 但是不是senator 或者2) d且senator的人不speak 推出的2）和上面的矛盾所以排除

由1）推出 senator不seaker

不知道说清楚了没有

ypngzhang · 发表于 2006-12-22 20:46:00

以下是引用tianwan在2004-4-3 11:11:00的发言：

No democrat both spoke at the convention and was a senator.除了表示 democrat either spoke or was a senator，还应该包括 democrat neither spoke nor was a senator.

也就是说：democrat1: speak, not senator;democrat2: not speak, senator; democrat3: not speak, not senator.
我被否定表示法弄糊涂了，请NN指正，我的理解是不是对的？

请教NN们，

1，我和tianwan的理解一样，这样是对还是错？

2，这道题到底怎么做啊？看了NN的回帖，还是不懂。

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