Help: LSAT SET 25, SECTION II 17,22,25

braveMBA · 发表于 2003-9-6 05:25:00

17. Wild cheetahs live in the African grasslands. Previous estimates of the size that the wild cheetah population must be in order for these animals to survive a natural disaster in the African grass lands region were too small, and the current population barely meets the previous estimates. At present, however, there is not enough African grassland to support a wild cheetah population larger than the current population.
The Statement above, if true, most strongly support which one of the following conclusions?
(A) Previous estimates of the size of the existing wild cheetah population were inaccurate.
(B) The cheetah’s natural habitat is decreasing in size at a faster rate than is the size of the wild cheetah population.
(C) The principal threat to the endangered wild cheetah population is neither pollution nor hunting, but a natural disaster.
(D) In the short term, the wild cheetah population will be incapable of surviving a natural disaster in the African grasslands.
(E) In regions where land is suitable for cheetah habitation, more natural disasters are expected to occur during the next decade than occurred during the past decade.

key: D. Why not A? I can not grasp the meaning of the subject. Please help!

22. Biologist: Some speculate that the unusually high frequency of small goats found in island populations is a response to evolutionary pressure to increase the number of goats so as to ensure a diverse gene pool. However, only the reproductive success of a trait influences its frequency in a population. So, the only kind of evolutionary pressure that can reduce the average size of the members of a goat population is that resulting from small goats achieving greater reproductive success than their larger cousins.
The biologist’s view, if true, provides the most support for which one of the following?
(A) The evolutionary pressure to ensure a diverse gene pool could have the effect of increasing the frequency of a gene for small size.
(B) The unusual frequency of small goats in island populations is not a result of the greater reproductive success small goats possess when space is limited.
(C) Contrary to what some believe, large goats achieve greater reproductive success than small goats even when space is limited.
(D) The evolutionary pressure to ensure a diverse gene pool does not have the effect of increasing the frequency of a gene for small size.
(E) A diverse gene pool cannot be achieved in a goat population unless the average size of its members is reduced.

KEY D. Could you please tell me the meaning of the passage?

25. A recent survey showed that 50 percent of people polled believed that elected officials should resign if indicted for a crime, whereas 35 percent believe that elected officials should resign only if they are convicted of a crime. Therefore, more people believe that elected officials should resign if indicted than believe that they should resign if convicted.
The reasoning above is flawed because it
(A) draws a conclusion about the population in general based only on a sample of that population
(B) confuses a sufficient condition with a required condition
(C) is based on an ambiguity of one of its terms
(D) draws a conclusion about a specific belief based on responses to queries about two different specific beliefs
(E) contains premises that cannot all be true

KEY: B. I can not understand, here, what is the SUFFICIENT CONDITION, and what is the REQUIRED CONDITION?

braveMBA · 发表于 2003-9-6 11:27:00

merlion · 发表于 2003-9-6 11:52:00

in 25:
premise: 50 percent of people polled believed :  indicted->resign
      35 percent believe :  resign->convicted

conclusion:  50% believe :  indicted->resign
            35% believe:  convicted-> resign

SUFFICIENT CONDITION:  充分条件
REQUIRED CONDITION: 必要条件

if a, b:  a->b, a is 充分条件, b is 必要条件
only if a, b: b->a, b is 充分条件, a is 必要条件

hope i said nothing wrong

braveMBA · 发表于 2003-9-6 12:00:00

Thanks MM. I mean what is the Sufficient Condition & Required Condition in the subject? Because I can not make any sense of B in 25. Why does author confuse a sufficient condition with a required condition?

merlion · 发表于 2003-9-6 12:33:00

前提使：35 percent believe : resign（充分条件）->convicted （必要条件）
结论是： 35% believe: convicted （充分条件）-> resign （必要条件）
作者从前提得结论时弄颠倒了。

don't take it wrong, i didn't mean you cann't figure out what is sufficient and what is required. just i answered some poster days ago about these questions, and two ppl replied that they didn't get what i was talking about, so i think i'd better make it clear this time. but it turns out i didn't, misleading ppl again.

hope others can help and make it clear.

[此贴子已经被作者于2003-9-6 15:47:19编辑过]

braveMBA · 发表于 2003-9-7 01:31:00

谢谢MM。别哭了。
我才注意到，是ONLY IF。

vrylwj · 发表于 2003-9-7 10:10:00

17. Previous estimates of the size that the wild cheetah population must be in order for these animals to survive a natural disaster in the African grass lands region were too small.

我想，这句话和最后草地供应的结论是两个方面。这句话科学家估计cheetah 的population太少了，不能survive a natural disater. 而现在实际上cheetah更少了。

vrylwj · 发表于 2003-9-7 10:21:00

22。
第一句说： response to evolutionary pressure 导致了 high frequency of small goats
第二句说： only the reproductive success 导致 frequency
结论：greater reproductive success 导致了 evolutionary pressure

braveMBA · 发表于 2003-9-7 12:14:00

Thanks, vrylwj(a strange name.)

vrylwj · 发表于 2003-9-7 12:20:00

thank you. I enjoy having the feeling of being different.

[此贴子已经被作者于2003-9-7 12:21:06编辑过]

Help: LSAT SET 25, SECTION II 17,22,25

Help: LSAT SET 25, SECTION II 17,22,25

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