mindfree,请帮帮忙！

marshial

Mindfree,阅读了几篇你的关于逻辑的大作，非常佩服！我在逻辑方面有一个问题一直没有搞清楚，就是充分（条件）性和必要（条件）性，如果只是从理论层面讲，我还是可以理解的，但具体到做题过程中却不能把握。我找了几道题，不知你能否给予解答?希望从你那里得到解这类题的方法！谢谢！！

45. Commissioner: Budget forecasters project a revenue shortfall of a billion dollars in the coming fiscal year. Since there is no feasible way to increase the available funds, our only choice is to decrease expenditures. The plan before you outlines feasible cuts that would yield savings of a billion dollars over the coming fiscal year. We will be able to solve the problem we face, therefore, only if we adopt this plan.
This reasoning in the commissioner’s argument is flawed because this argument
(A) relies on information that is far from certain
(B) confuses being an adequate solution with being a required solution
(C) inappropriately relies on the opinions of experts
(D) inappropriately employs language that is vague
(E) takes for granted that there is no way to increase available funds


If the city council institutes new parking regulations, city revenues will surely increase, since studies have conclusively shown that, if such parking regulations are put into effect, there is an increase in parking violations, and an increase in parking violations will result in a greater number of parking fines collected.

64. If the statements in the passage are true, which one of the following must also be true?
(A) Unless there is an increase in the number of parking violations in the city, city revenues will not increase.
(B) If the city council institutes new parking regulations, the council will fall from favor with the citizens.
(C) The city council will institute new parking regulations only if an increase in city revenues can be expected to result.
(D) If the city council’s new regulations cause more parking violators to be ticketed, the city revenues will increase.
(E) Unless the city institutes a complex system of parking regulations, the city cannot expect traffic violations to increase.
尤其这道题目，我觉得C、D都对，不知如何甄选。

nickynicky

第一道题我选A,第二道题我觉得是D吧？
如果我做的答案对的话，我给你解释解释。呵呵。

fyhllj

http://forum.chasedream.com/dispbbs.asp?boardID=24&ID=19876

看看这个市同一类型的题

Michael1975

我选择1. E;   2.D
对吗?

cranberry

第1是B，第2是D

mindfree

Hi,

Sorry that I could not come here these days and could not answer questions...

1. B
If X, then Y ==> X is the sufficient (adequate) condition to Y
Only if X, then Y ==> X is the required condition to Y ==> Y-->X

The flaw is that the plan is sufficient to solve the budget problem by cutting spending (if plan --> problem solved). However, the conclusion is only if we adopt the plan, we will solve the problem (problem solved --> plan)

So the conclusion is not based on the premises.

Required condition means that the condition has to be true for the conclusion. For example, only if you go (X), I will go (Y)==> If I did go (Y), you must have gone too (X).

Can you tell the difference? Let me know

2. D
"Unless" and "only if" always indicate required condition. When the question reads like if (when) A, then B, the reasoning is not equal to only if (unless) A, then (not) B. The first is sufficient, while the second is required.

For example, Eating rice, you will be full. The argument does not equal to "only if you eat rice, you will be full". The argument simply say eating rice will result in fullness. It does not rule out other means.

Let me know if you got the points

marshial

谢谢，mindfree,看了你的帖子，很的收获，多谢！！