L1994/2-4-24逻辑题望高手指教

jameshoo

24. When the rate of inflation exceeds the rate of return on the most profitable investment available, the difference between those two rates will be the percentage by which, at a minimum, the value of any investment will decline. If in such a circumstance the value of a particular investment declines by more than that percentage, it must be true that________

Which one of the following logically completes the argument?

(A) The rate of inflation has risen.

(B) The investment in question is becoming less profitable.

(C) The investment in question is less profitable than the most profitable investment available.

(D) The rate of return on the most profitable investment available has declined.

(E) There has been a change in which particular investment happens to be the most profitable available.
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答案C

Hades整理的逻辑题解释中给的解释是：

“文中讲，这个pecentage最少也是通涨率超过最赚钱的投资的回报率的部分，如果一个投资的回报率少于最赚钱的回报率，则它的回报率和通涨率之间的差距一定会大于那个PECENTAGE所以跌价的幅度就更大。”

只有这个解释的逆命题正确才能推出答案C（但一个命题的逆命题不一定正确），因此不是令人满意的解释。

我的问题是：

题目说通货膨胀率减去最赚钱的投资的回报率等于任何一项投资最少会有的贬值率（不知有没有曲解)。然后又提出有一项投资的贬值率比刚才的那个贬值率大，问可以推出什么结论。

实在令人费解，望高人指点。

[此贴子已经被作者于2006-10-4 21:56:46编辑过]

贺赫赫盒

定义：r(i)=通货膨胀率；
          r(p)=某一产品的投资回报率即 rate of return on investment
          r(p, max)=所有产品中最高回报产品的回报率即 rate of return on most profitable investment；
          △r(p)=某一产品价值减少的比率即 the percentage by which the value of a investment will decline;
          △r(p,min)=所有产品中价值减少的比率的最小值即 the percentage by which, at a minimum, the value of any investment will decline.

由题目的第一句话，可以得到：r(i)-r(p, max)=△r(p,min)；即通货膨胀率减去所有产品中最高回报产品的投资回报率等于所有产品中投资回报率将会减少的最小值。
第二句话说，现在有一个产品，它的产品回报率减少的比率小于所有产品中投资回报率将会减少的最小值，即△r(p)>△r(p,min)。
将公式二代入公式一中可以得到：r(i)-r(p)=△r(p)，把它和公式一比较可以知道r(i)不变，△r(p)>△r(p,min)，那么相应的r(p)<r(p, max)。也就是该产品的投资回报率小于the most profitable investment 的回报率，也就是C选项的内容。

LZ应该是将 △r(p,min)=所有产品中贬值率的最小值曲解为了任何一项投资最少会有的贬值率。
这道题通过题目条件列出公式，线索就会很清晰。

Bensontuo

贺赫赫盒 发表于 2020-3-29 19:49
定义：r(i)=通货膨胀率；
          r(p)=某一产品的投资回报率即 rate of return on investment
          ...

I have a different idea. Perhaps its better for some of you, and please feel free to take a look.

Question type: Must be true.

Argument:

If A of Z1 > B of Z1, then C, quantified digitally as the differences between A of Z1  and B of Z1, is the minimum percentage of any investment will decline. { Z1* C = depreciation of Z1}

If D exist, and we know that D equals to the differences between A of y1 and b of y 1, and A, rate of inflation, must be the same for both Z1 and Y1. Plus, D > C . Then what must be true ?

*B must > b ( rate of return on the Most profitable investment available = B )

A. The rate of inflation has risen ? No, no way can we infer that from the passage.

B. By logically competing the argument, we want to connect the core, and apparently, the core is definitely not whether an investment would be " becoming less profitable " or not. The core of the argument is the " how to define the necessary assumption " . It's a premise booster.

C. If D > C, then B must > b, and If b < B, then the ROI of Z1 must > ROI of Y1 ), since A ( Rate of inflation should be the same for any investments ) Correct ANSWER

D. What if C = 0 and D = 1 ? Is that even possible ? hell ya. No any restrictions nor limitation to regulate C should not be zero and happened that D still bigger than C. If C = 0, then Z1's depreciation value is also 0. Not true at all.

E. Regardless of if there is change or not, under the condition of D > C,  B will always > b, it could be true its not Z1 no more, it could be U1, W1, O1. However, it also not require to be changed either.

Isn't that way easier ?