mammals, guitars...

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mammals, guitars...

by yangliu0401 » Mon Mar 30, 2009 2:39 pm
1. Although most species of nondomestic mammals in Australia are marsupials, over 100 species- including seals, bats, and mice-are not marsupials but placentals. It is clear, however, that these placentals are not native to this island continent: all nonhuman placentals except the dingo, a dog introduced by the first humans that settled Australia, are animals whose ancestors could swim tong distances, fly, or float on driftwood.

The conclusion above is properly drawn if which one of the following is assumed?

(A) Some marsupials now found in Australia might not be native to that continent, but rather might have been introduced to Australia by some other means.

(B) Humans who settled Australia probably introduced many of the placental mammal species now present on that Continent.

(C) The only Australian placentals that could be native to Australia would be animals whose ancestors could not have reached Australia from elsewhere.

(D) No marsupials now found in Australia can swim long distances. fly. or float on driftwood.

(E) Seals, bats, and mice are typically found only in areas where there are no native marsupials.

OA is C, while I choose D

2. Jane: Professor Harper's ideas for modifying the design of guitars are of no value because there is no general agreement among musicians as to what a guitar should sound like and. Consequently, no widely accepted basis for evaluating the merits of a guitar's sound.

Mark: What's more, Harper's ideas have had enough time to be adopted if they really resulted in superior sound. It took only ten years for the Torres design for guitars to be almost universally adopted because of the improvement it makes in tonal quality.

Which one of the following most accurately describes the relationship between Jane's argument and Mark's argument?

(A) Mark's argument shows how a weakness in Jane's argument can be overcome.

(B) Mark's argument has a premise in common with Jane's argument

(C) Mark and Jane use similar techniques to argue for different conclusions.

(D) Mark's argument restates Jane's argument in other terms.

(E) Mark's argument and Jane's argument are based on conflicting suppositions.

OA is E, while I choose D

So confused!!!Pls help me out!
Source: — Reading Comprehension |

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Critical Reasoning Help

by Jose Ferreira » Wed Apr 01, 2009 1:07 pm
Hi Yangliu,

Let's tackle that first problem by using what we know about most logical GMAT arguments: Valid conclusions must be supported by explicit premises (evidence) and implicit premises (assumptions).

Reading the question stem first (a technique employed by quite a few test takers) we should correctly identify this as an assumption question. Assumption questions ask us to identify information that's necessary to the argument but is not stated. One of the easier ways of finding assumptions is to single out the conclusion and the evidence and look for holes in the reasoning connecting them.

The conclusion: It is clear, however, that these placentals are not native to this island continent.

A quick note about this conclusion: Whenever an author concludes that something is obvious or clear, it should raise an immediate red flag. In such cases, the author is almost always overlooking something. In this case, since it's an assumption question, we expect the author to be overlooking something that must be true... the assumption. So, if we can discover what the author is taking for granted here, we should have our answer.

The evidence should tell us why the author believes the conclusion to be true. In this case, the author points to the fact that ancestors of all nonhuman placentals (except the dingo, which was brought to Australia by humans) were capable of swimming long distances, flying, or floating on driftwood.

Let's ignore the first sentence about the types of species found in Australia, as it is simply background detail used to define placentals and has little bearing on the argument.

The author's argument is as follows:

Since all of the placentals found in Australia are descendants of animals that could swim, fly, or float long distances, they must not be native to Australia.

Does this logic seem complete to you?

The author is relying on the idea that in order for something to be native to Australia its ancestors must not have had the ability to travel long distances (i.e. the ability to have reached the continent from somewhere else).

This is what answer choice "C" says.

Answer choice "D" addresses marsupials, which I concede can be confusing. However, if we agree marsupials are simply mentioned in the first sentence in order to define placentals, then they are outside the scope of the author's argument. It's irrelevant that there aren't marsupials now found in Australia that can swim long distances. The author's conclusion is about placentals, and does not rely on how marsupials got to the continent. In fact, the author does not address whether marsupials are native to Australia at all.
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by anshulseth » Sat Apr 04, 2009 10:32 pm
Regarding Q2:
The premise on which the conclusion is based is diff for Jane than Mark.
Jane bases it on no value of Harper's ideas based on the supposition that there is no consensus on "how the guitar should sound like".

Mark has the same conclusion but actually talks about the quality of sound.
So he supposes if the music is good. it should have evolved a better sound all this while, which is diff than that of Jane.

Thus E.
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by cramya » Sat Apr 04, 2009 10:47 pm
Thanks for a good explanation Jose!

Yangliu,
Ques (1)

In addition before u pick a choice for assumption question try negating that choice and see if it weakens the argument.

If u negate C then the conclusion that Jose had explained as being present in the argument falls apart.

An assumption is something that must be true (author has believed in but not stated) for the conclsuion to stand.

Hope this helps too.

Regards,
CR