Re: Verbal Chat with a Tutor every Wednesday at 7:30 AM PST/8 PM IST
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15 Oct 2017, 11:05
Chat Transcript: 10/11/17
Q:Geologist: The dominant view that petroleum formed from the fossilized remains of plants and animals deep in the earth’s crust has been challenged by scientists who hold that it formed, not from living material, but from deep carbon deposits dating from the formation of the earth. But their theory is refuted by the presence in petroleum of biomarkers, molecules indicating the past or present existence of a living organism.
Which one of the following, if true, most weakens the geologist’s argument?
(A) Fossils have been discovered that are devoid of biomarkers.
(B) Living organisms only emerged long after the earth’s formation.
(C) It would take many millions of years for organisms to become petroleum.
(D) Certain strains of bacteria thrive deep inside the earth’s crust.
(E) Some carbon deposits were formed from the fossilized remains of plants.
Source: LSAT
A:we have a weaken question, so job #1 is to find the conclusion. Basically, the conclusion is "their theory is refuted by the presence in petroleum of biomarkers, molecules indicating the past or present existence of a living organism."Next thing is probably to figure out what, exactly, is the theory that "is refuted". We’re basically talking about refuting the scientists’ theory at the end of the first sentence: "scientists who hold that it formed, not from living material, but from deep carbon deposits dating from the formation of the earth." And just to make this totally confusing: the scientists’ theory challenges the "dominant view that petroleum formed from the fossilized remains of plants and animals..."So this is a hot mess: dominant view is challenged by the scientists, and then the scientists’ view is "refuted" by the geologist.Basically, the geologist is supporting the dominant view: that petroleum formed from the fossilized remains of plants and animals. Evidence: petroleum contains biomarkers that indicate present or past existence of a living organism. And we’re trying to weaken the geologist’s argument -- or, equivalently, strengthen the scientists’ claim that petroleum is formed from deep carbon deposits dating from the formation of the earth.I think we can happily eliminate (A). The issue is that petroleum DOES contain biomarkers -- suggesting the presence of an organism. The fact that there are fossils without biomarkers certainly doesn’t help us weaken the conclusion.(B) is totally irrelevant. It doesn’t really matter when living organisms showed up on earth -- we’re interested in figuring out whether petroleum is made from the little buggers, not WHEN life began on this planet.(C) is also irrelevant. Sure, it would take millions of years. But that wouldn’t do anything to help us figure out whether petroleum is made from living things, or from carbon from the early days of the earth.(D) is tough, but it might actually weaken the argument. If the scientists -- with their theory that petroleum comes from carbon from the formation of the earth, not living creatures -- are right, then we have to find a way to explain why those biomarkers DON’T actually refute their theory. And (D) would do the trick: the petroleum from deep in the earth’s crust could be formed by carbon from the earth’s formation -- in contrast to the geologist’s argument -- and the bacteria are just some "pollution" that has nothing to do with how the petroleum was formed. It’s subtle, but (D) would weaken the geologist’s claim.(E) is irrelevant, because we’re not really concerned about the formation of "some carbon deposits." We’re trying to figure out how petroleum -- a very specific carbon-based substance -- is made. So the answer is (D).
Q: Pertaining to above argument, how can bacteria weaken the argument of biomarker?
A: bacteria are alive! Let’s come back to the scientists’ opinion: "scientists who hold that it formed, not from living material, but from deep carbon deposits dating from the formation of the earth." If there are bacteria "deep inside the earth’s crust", as (D) says, then it’s possible that the scientists are right: petroleum was formed from deep carbon deposits, and the bacteria down there had nothing to do with the formation of the petroleum. The bacteria are just hitching a ride with the petroleum -- and that would explain why there are biomarkers, without undermining the view that the petroleum isn’t actually formed from living things. In other words: (D) gives us a case in which the biomarkers are in the petroleum, but really don’t indicate what the geologist thinks they indicate.Option D definitely casts doubt on the geologist’s conclusion. Geologist draws a direct link from biomarkers to the origins of petroleum; if there’s an alternate explanation for the biomarkers, it weakens the geologist’s argument.
Q: are percentage questions frequent on GMAT. any tactics you advice for %tage and hard numbers together in argument
A: You’ll almost never see a verbal question that requires you to do any real thinking about percentages. Sure, you’ll occasionally see a number or a percentage in a CR question, but a lot of test-prep companies write very mathematical CR questions... and those don’t actually exist on the actual exam.
Q:The percentage of households with an annual income of more than $40,000 is higher in Merton county than in any other county. However, the percentage of households with an annual income of $60,000 or more is highest in Sommer county.
If the statements above are true, which of the following can properly be concluded on the basis of them?
A. No household in Merton county has an annual income of $60,000 or more.
B. Some households in Merton county have an annual income between $40,000 and $60,000.
C. The number of households with an annual income of more than $40,000 is greater in Merton than in Sommer county.
D. Average annual household income is higher in Sommer than in Merton county.
E. The percentage of households with an annual income of $80,000 is higher in
Sommer than in Merton county.
A: Basically, we’re trying to resolve a discrepancy of sorts: how is that Merton county has a higher percentage of households with annual income of $40,000+ than "any other county," but the percentage of households with $60,000+ incomes is higher in Sommer? The question asks us to find something that can be concluded based on these facts -- but the facts seem almost contradictory.You definitely can’t conclude (A): there certainly could be at least one household with an annual income of $60,000+(B) seems pretty good -- of course there would have to be some households in Merton with $40-$60,000 incomes, or else it would be impossible for Merton to be #1 in incomes over $40,000, but behind Sommer county in the percentage of households with $60,000+ incomes. And notice the deliberately weak language here: "SOME households..." Sure, that seems true enough.(C) switches us from percentage to NUMBER. The entire passage talks about the percentage of households, but we can’t make any sort of conclusions about the number of households unless we know something about the relative size of the counties.(D) We can’t conclude this one, either. Knowing something about the relative percentages of high-income households doesn’t allow us to say anything definitive about overall average incomes. A single Warren Buffet type can skew the whole thing pretty severely, for example(E) We don’t know anything about households over $80,000. So we’re left with (B). Key word: "some."
Q: do you always ’dislike’ extreme words in inference answer choices?
A: Does this strategy work good for assumption Qs too (esp word should in answer choices)" The answer is a very strong no. "Extreme" words should always catch your eye immediately, because they’re useful. It’s pretty easy to prove or disprove something if the language is extreme. But there’s no reason why extreme language is necessarily wrong. For example, extreme language can be exactly the BEST way to strengthen or weaken an argument.Put another way: extreme language is wrong about 80% of the time on CR. So is everything else
Q: Tip to handle EXCEPT Qs:
A: you’ll want to start by writing the following, with the blank filled in: "Cross out anything that _____________" The most common error I see on EXCEPT questions is that you’ll start out just fine. Let’s suppose that the question says "each of the following would strengthen the argument EXCEPT." You’ll knock down two or three answer choices that strengthen. And then when you start going back and forth between the last few choices, you’ll start racking your brain to figure out which one of the final answers strengthen. And you’ll go back and forth, and back and forth. And let’s say that you’re down to (B) and (D), and it’s really hard. And then you get it! (B) strengthens! So (B) is your answer! Except that it isn’t: (D) would be the winner in that case. So make sure that the phrase "cross out anything that _______" is looking you square in the eye
close
For most of our students? If I’m at all worried that they’ll get nervous, I think they should use the original order.
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