经典经典的逻辑题~欢迎讨论~

薇洋祈轩

~~~（1）Manatees, aquatic mammals inhabiting Florida’s rivers and coastal waters, swim close to the surface and are frequently killed in collisions with boats.  To address the problem, boat traffic in manatee-populated waters is being required to maintain very low speeds.  Unfortunately, manatees are unable to hear low-pitched sounds and a boat’s sound lowers in pitch as the boat slows.  Therefore, this approach may in fact make things worse rather than better.
Which of the following, if true, casts most doubt on the conclusion?
A.    The areas where boats would have to maintain low speeds were decided partly on the basis of manatee-population estimates and partly from numbers of reported collisions between manatees and boats.
B.    Because the water hyacinth that manatees feed on grows best in water that is nearly still, water hyacinth beds can be disturbed or damaged by fast-moving boat traffic.
C.    Over the last several decades, boat traffic in Florida’s coastal waters has been increasing almost continuously and now represents the greatest threat to the endangered manatee population.
D.    The sound of a boat engine generally travels much further under water than it does through the air.
E.    When experimenters exposed manatees to the recorded sounds of boats moving at various speeds, the creatures were unable to discern the sounds over normal background noise.



~~~（2）28. GWD28-Q28:
Which of the following most logically completes the argument?
A certain cultivated herb is one of a group of closely related plants that thrive in soil with high concentrations of metals that are toxic to most other plants.  Agronomists studying the herb have discovered that it produces large amounts of histidine, an amino acid that, in test-tube solutions, renders these metals chemically inert.  ossibly, therefore, the herb’s high histidine production is what allows it to grow in metal-rich soils, a hypothesis that would gain support if ______.
A.    histidine is found in all parts of the plant—roots, stem, leaves, and flowers
B.    the herb’s high level of histidine production is found to be associated with an unusually low level of production of other amino acids
C.    others of the closely related group of plants are also found to produce histidine in large quantities
D.    cultivation of the herb in soil with high concentrations of the metals will, over an extended period, make the soil suitable for plants to which the metals are toxic
E.    the concentration of histidine in the growing herb declines as the plant approaches maturity
（答案是C 但是我倾向于D）

38: GWD-29-Q35
In Patton City, days are categorized as having heavy rainfall (more than two inches), moderate rainfall (more than one inch, but no more than two inches), light rainfall (at least a trace, but no more than one inch), or no rainfall.  In 1990, there were fewer days with light rainfall than in 1910 and fewer with moderate rainfall, yet total rainfall for the year was 20 percent higher in 1990 than in 1910.
If the statements above are true, then it is also possible that in Patton City
A.    the number of days with heavy rainfall was lower in 1990 than in 1910
B.    the number of days with some rainfall, but no more than two inches, was the same in 1990 as in 1910
C.    the number of days with some rainfall, but no more than two inches, was higher in 1990 than in 1910
D.    the total number of inches of rain that fell on days with moderate rainfall in 1990 was more than twice what it had been in 1910
E.    the average amount of rainfall per month was lower in 1990 than in 1910
（这题要非常非常非常注意！！！）

dengyichao

第一题：要注意攻击对象。
文章中得出了让船只速度下降只会让情况变得更糟的结论，是因为Manatees受不了船只慢行时发出的低频声波。
为了要削弱文章结论，必须攻击“Manatees受不了船只慢行时发出的低频声波”这一点
E说，Manatees在噪音中是无法分辨声音的，所以即使船只慢行会发出低频音波，也不会对Manatees造成负面影响，削弱了文章结论。说明是船只慢行就可以起到保护Manatees的作用的。
而B说，Manatees吃的食物会被快速行驶的船只破坏，那么让船只慢行的确可以保护Manatees，但是低频声波的问题仍然不容忽视，无法削弱文章结论

dengyichao

第二题：同样要注意攻击对象。
文章问的是下面哪个可以支持一个假说，什么假说呢，the herb之所以可以在金属含量很高的土壤里生长时因为他又高产量的histidine。
D说the herb经过一段时间的培养可以使得金属含量很高的土壤适合其他植物生长。这只能说the herb的确有一种方法可以起到降低金属浓度之类的作用，但是这跟高产量的histidine有什么关系呢。
C采用的是类比的方法，其他能在金属含量高的土壤里的植物也有高产量的histidine，很好地支持了这个假说。
一定要理解文章意思，迅速找出什么是原因，什么是结果。

dengyichao

这题说，有四种雨量heavy rainfall，moderate rainfall，light rainfal，no rainfall，1990年跟1910年比，moderate rainfall和light rainfal的天数都较少，但是总雨量大20%。
D：moderate rainfall的范围是（1，2）所以1990年一天的雨量再大也会小于1910年的2倍，而天数又少，所以moderate rainfall的总雨量还是小于1910年的2倍。错
E：一年的月份一样多，所以1990年的平均雨量比1910年的平均雨量大。错
至于ABC,我也想不到怎么排除
期待牛人解答，GWD果然难啊。。。

dengyichao

哦，BC说的是小于two inches的下雨天，只要moderate rainfall和light rainfal的天数加起来就行了。
题目里已经说了moderate rainfall和light rainfal的天数加起来1990年比1910年小，所以明显选A了

dengyichao

我以为还要加上no rainfall，糊涂了，这里有更详细的解释。
http://forum.chasedream.com/GMAT_CR/thread-177002-1-1.html
大家越解释越复杂，我觉得我想的比较简单，理解就好，希望能帮到你

薇洋祈轩

Which of the following, if true, casts most doubt on the conclusion?
A.    The areas where boats would have to maintain low speeds were decided partly on the basis of manatee-population estimates and partly from numbers of reported collisions between manatees and boats.
B.    Because the water hyacinth that manatees feed on grows best in water that is nearly still, water hyacinth beds can be disturbed or damaged by fast-moving boat traffic.
C.    Over the last several decades, boat traffic in Florida’s coastal waters has been increasing almost continuously and now represents the greatest threat to the endangered manatee population.
D.    The sound of a boat engine generally travels much further under water than it does through the air.
E.    When experimenters exposed manatees to the recorded sounds of boats moving at various speeds, the creatures were unable to discern the sounds over normal background noise.
this approach may in fact make things worse rather than better.

题目结论指出低速比变速糟糕

manatees are unable to hear low-pitched sounds and a boat’s sound lowers in pitch as the boat slows.  

题目情景指出低速情况不能听见声音

the creatures were unable to discern the sounds over normal background noise.

题支E指出变速情况不能听见声音



意思是不是低速和变速的情况一样糟糕并没有改变。所以E为正解。

薇洋祈轩

Which of the following most logically completes the argument?
A certain cultivated herb is one of a group of closely related plants that thrive in soil with high concentrations of metals that are toxic to most other plants.  Agronomists studying the herb have discovered that it produces large amounts of histidine, an amino acid that, in test-tube solutions, renders these metals chemically inert.  ossibly, therefore, the herb’s high histidine production is what allows it to grow in metal-rich soils, a hypothesis that would gain support if ______.

D.    cultivation of the herb in soil with high concentrations of the metals will, over an extended period, make the soil suitable for plants to which the metals are toxic



the herb’s high histidine production is what allows it to grow in metal-rich soils

题目结论——histidine 导致grow in metal-rich soils“因为histidine renders these metals chemically inert”

那么我们要获得的支持就是论证“因为”部分——D选项充分论证了“因为”部分。

所以我强烈认为答案有误——应该是D

薇洋祈轩

38: GWD-29-Q35
In Patton City, days are categorized as having heavy rainfall (more than two inches), moderate rainfall (more than one inch, but no more than two inches), light rainfall (at least a trace, but no more than one inch), or no rainfall.  In 1990, there were fewer days with light rainfall than in 1910 and fewer with moderate rainfall, yet total rainfall for the year was 20 percent higher in 1990 than in 1910.
If the statements above are true, then it is also possible that in Patton City
A.    the number of days with heavy rainfall was lower in 1990 than in 1910
B.    the number of days with some rainfall, but no more than two inches, was the same in 1990 as in 1910
C.    the number of days with some rainfall, but no more than two inches, was higher in 1990 than in 1910
D.    the total number of inches of rain that fell on days with moderate rainfall in 1990 was more than twice what it had been in 1910
E.    the average amount of rainfall per month was lower in 1990 than in 1910

B选项 思考对立面
两年的no more than two inches相同
两年的heavy rainfall 相同。
加上“fewer days with light rainfall than in 1910 and fewer with moderate rainfall”
与” total rainfall for the year was 20 percent higher in 1990 than in 1910.”矛盾

C选项 思考对立面
两年的no more than two inches 1990比1910高
两年的heavy rainfall 1990比1910低
加上“fewer days with light rainfall than in 1910 and fewer with moderate rainfall”
与” total rainfall for the year was 20 percent higher in 1990 than in 1910.”矛盾

D选项 极值考虑
moderate rainfall (more than one inch, but no more than two inches)
1990=2inch ，1910=1inch 为最大差距
加上“fewer days with light rainfall than in 1910 and fewer with moderate rainfall”
推出 1990=2inch*少的天数 VS 1910=1inch*多的天数
显然1990=2inch*少的天数 不会多于两倍的 1910=1inch*多的天数

E选项 直观
1990月均少 则整年少。
与” total rainfall for the year was 20 percent higher in 1990 than in 1910.”矛盾

A选项怎么感觉和C选项意思是一样的。

dengyichao

38: GWD-29-Q35
In Patton City, days are categorized as having heavy rainfall (more than two inches), moderate rainfall (more than one inch, but no more than two inches), light rainfall (at least a trace, but no more than one inch), or no rainfall.  In 1990, there were fewer days with light rainfall than in 1910 and fewer with moderate rainfall, yet total rainfall for the year was 20 percent higher in 1990 than in 1910.
If the statements above are true, then it is also possible that in Patton City
A.    the number of days with heavy rainfall was lower in 1990 than in 1910
B.    the number of days with some rainfall, but no more than two inches, was the same in 1990 as in 1910
C.    the number of days with some rainfall, but no more than two inches, was higher in 1990 than in 1910
D.    the total number of inches of rain that fell on days with moderate rainfall in 1990 was more than twice what it had been in 1910
E.    the average amount of rainfall per month was lower in 1990 than in 1910

B选项 思考对立面
两年的no more than two inches相同
两年的heavy rainfall 相同。
加上“fewer days with light rainfall than in 1910 and fewer with moderate rainfall”
与” total rainfall for the year was 20 percent higher in 1990 than in 1910.”矛盾

C选项 思考对立面
两年的no more than two inches 1990比1910高
两年的heavy rainfall 1990比1910低
加上“fewer days with light rainfall than in 1910 and fewer with moderate rainfall”
与” total rainfall for the year was 20 percent higher in 1990 than in 1910.”矛盾

D选项 极值考虑
moderate rainfall (more than one inch, but no more than two inches)
1990=2inch ，1910=1inch 为最大差距
加上“fewer days with light rainfall than in 1910 and fewer with moderate rainfall”
推出 1990=2inch*少的天数 VS 1910=1inch*多的天数
显然1990=2inch*少的天数 不会多于两倍的 1910=1inch*多的天数

E选项 直观
1990月均少 则整年少。
与” total rainfall for the year was 20 percent higher in 1990 than in 1910.”矛盾

A选项怎么感觉和C选项意思是一样的。

-- by 会员 薇洋祈轩 (2010/3/13 20:14:00)

你犯了之前跟我一样的错误，BC的排除没有那么复杂the number of days with some rainfall, but no more than two inches的天数就是moderate rainfall和light rainfall的天数之和，不包括nonrainfall的天数（我前面已经说了这点了）
文章已经说了1990年的moderate rainfall和light rainfall的天数都是fewer，所以不管是说一样，还是说小于都属于跟原文意思相悖