GMAT Critical Reasoning Discussions

MBA
2284
The single idea that is the most useful in Critical Reasoning on the GMAT is the Contrapositive. Heres how to form a contrapositive:

Step 1: Start out with a cause/effect statement. This is best done in the if/then format. Heres our example: If you are a fish, then you live in water. This statement is arguably true (with the exception of mudskippers, but thats debatable!).

Step 2: Now, reverse the elements of your statement: If you live in water, then you are a fish. This statement is not NECESSARILY true. Many other, non-fish organisms live in water as well, like whales, seaweed, crustaceans, and plankton.

Step 3: Negate both sides of the statement: If you dont live in water, then you are not a fish. This statement is equally true as the original statement. It is the CONTRAPOSITIVE!

When you have complex statements, that involve and or or, you must switch them around. For example, the contrapositive of If you are at least 18 years old and registered, then you can vote is If you cant vote, then you are not at least 18 years old OR not registered. If one of those two elements is missing, the person cannot vote. Simple, really!

Now, lets apply our knowledge of the contrapositive to a Critical Reasoning question, and see why its so useful:

The interview is an essential part of a successful hiring program because, with it, job applicants who have personalities that are unsuited to the requirements of the job will be eliminated from consideration.

The argument above logically depends on which of the following assumptions?

(A) A hiring program will be successful if it includes interviews.

(B) The interview is a more important part of a successful hiring program than is the development of a job description.

(C) Interviewers can accurately identify applicants whose personalities are unsuited to the requirement of the job.

(D) The only purpose of an interview is to evaluate whether job applicants personalities are suited to the requirements of the job.

(E) The fit of job applicants personalities to the requirements of the job was once the most important factor in making hiring decisions.


When we look at the question stem, its clear that were looking for a necessary assumption, or an assumption upon which the success of the argument depends. Lets break the argument down into a formal logic statement. Our keyword here is because that means we need to switch the order of the arguments elements. Here it is:
If job applicants with unsuitable personalities can be eliminated from consideration, then interviews are essential.
Now, make your contrapositive.
If interviews are NOT essential, then job applicants with unsuitable personalities CANNOT be eliminated from consideration.
What does this mean to us? This means that if the authors argument is in favor of interviews, and his proof is that interviews weed out unsuitable people, we must then select an answer choice that makes this argument entirely waterproof. That means that answer choice (C) is the correct answer.
2285

No one knows what purposes, if any, dreams serve, although there are a number of hypotheses. According to one hypothesis, dreams are produced when the brain is erasing "parasitic connections" (meaningless, accidental associations between ideas), which accumulate during the day and which would otherwise clog up our memories. Interestingly, the only mammal that does not have rapid eye movement sleep, in which we humans typically have our most vivid dreams, is the spiny anteater, which has been seen as anomalous in that it has a very large brain relative to the animal's size. This fact provides some confirmation for the parasitic-connection hypothesis, since the hypothesis predicts that for an animal that did not dream to have an effective memory that animal would need extra memory space for the parasitic connections.
The parasitic-connection hypothesis, if true, most strongly supports which one of the following?
(A) The animals with the smallest brains spend the most time sleeping.
(B) Immediately after a person awakens from normal sleep, her or his memory contains virtually no accidental associations between ideas.
(C) When a mammal that would normally dream is prevented from dreaming, the functioning of its memory will be impaired.
(D) Insofar as a person's description of a dream involves meaningful associations between ideas, it is an inaccurate description.
(E) All animals other than the spiny anteater dream.

2286

I would go in for C as I feel it supports the hypothesis. Others please chip in with your choice.

Naren, please let me know what the right answer for this is.

2287
No one knows what purposes, if any, dreams serve, although there are a number of hypotheses. According to one hypothesis, dreams are produced when the brain is erasing parasitic connections (meaningless, accidental associations between ideas), which accumulate during the day and which would otherwise clog up our memories. Interestingly, the only mammal that does not have rapid eye movement sleep, in which we humans typically have our most vivid dreams, is the spiny anteater, which has been seen as anomalous in that it has a very large brain relative to the animals size. This fact provides some confirmation for the parasitic-connection hypothesis, since the hypothesis predicts that for an animal that did not dream to have an effective memory that animal would need extra memory space for the parasitic connections.
The parasitic-connection hypothesis, if true, most strongly supports which one of the following?
(A) The animals with the smallest brains spend the most time sleeping.
(B) Immediately after a person awakens from normal sleep, her or his memory contains virtually no accidental associations between ideas.
(C) When a mammal that would normally dream is prevented from dreaming, the functioning of its memory will be impaired.
(D) Insofar as a persons description of a dream involves meaningful associations between ideas, it is an inaccurate description.
(E) All animals other than the spiny anteater dream.


D seems to be better option and could be supported strongly from passage. Other options have loopholes like activity of brain, numbers of parasitic connection and amount of sleep required to erase those connections.

Whats the OA?
2288
No one knows what purposes, if any, dreams serve, although there are a number of hypotheses. According to one hypothesis, dreams are produced when the brain is erasing "parasitic connections" (meaningless, accidental associations between ideas), which accumulate during the day and which would otherwise clog up our memories. Interestingly, the only mammal that does not have rapid eye movement sleep, in which we humans typically have our most vivid dreams, is the spiny anteater, which has been seen as anomalous in that it has a very large brain relative to the animal's size. This fact provides some confirmation for the parasitic-connection hypothesis, since the hypothesis predicts that for an animal that did not dream to have an effective memory that animal would need extra memory space for the parasitic connections.
The parasitic-connection hypothesis, if true, most strongly supports which one of the following?
(A) The animals with the smallest brains spend the most time sleeping.
(B) Immediately after a person awakens from normal sleep, her or his memory contains virtually no accidental associations between ideas.
(C) When a mammal that would normally dream is prevented from dreaming, the functioning of its memory will be impaired.
(D) Insofar as a person's description of a dream involves meaningful associations between ideas, it is an inaccurate description.
(E) All animals other than the spiny anteater dream.

My take is D, which talks directly abt the hypothesis.
2289
No one knows what purposes, if any, dreams serve, although there are a number of hypotheses. According to one hypothesis, dreams are produced when the brain is erasing parasitic connections (meaningless, accidental associations between ideas), which accumulate during the day and which would otherwise clog up our memories. Interestingly, the only mammal that does not have rapid eye movement sleep, in which we humans typically have our most vivid dreams, is the spiny anteater, which has been seen as anomalous in that it has a very large brain relative to the animals size. This fact provides some confirmation for the parasitic-connection hypothesis, since the hypothesis predicts that for an animal that did not dream to have an effective memory that animal would need extra memory space for the parasitic connections.
The parasitic-connection hypothesis, if true, most strongly supports which one of the following?
(A) The animals with the smallest brains spend the most time sleeping.
(B) Immediately after a person awakens from normal sleep, her or his memory contains virtually no accidental associations between ideas.
(C) When a mammal that would normally dream is prevented from dreaming, the functioning of its memory will be impaired.
(D) Insofar as a persons description of a dream involves meaningful associations between ideas, it is an inaccurate description.
(E) All animals other than the spiny anteater dream.


OA is C.

(A) The animals with the smallest brains spend the most time sleeping. ---> Irrelevant. Nothing has been discussed about duration of sleeping time; only dreams have been discussed.

(B) Immediately after a person awakens from normal sleep, her or his memory contains virtually no accidental associations between ideas. ---> Not necessarily true. Its going to an extreme (virtually no accidental).

(C) When a mammal that would normally dream is prevented from dreaming, the functioning of its memory will be impaired. ---> Very true. The hypothesis states that extra memory space will be required by animals who do not dream in order to ensure that they have an effective memory. In this option, we will not assume that the mammal its talking about has an extra memory space. So, if we apply this hypothesis in general, then option C will be most strongly supported.

(D) Insofar as a persons description of a dream involves meaningful associations between ideas, it is an inaccurate description. ---> Not necessarily true. Its not written that a person can only dream of meaningless, accidental associations between ideas; he might dream something meaningful.

(E) All animals other than the spiny anteater dream. ---> Usage of extreme word (All animals). Excerpt discusses only mammals.
2290

Which book are you referring to??

2291
OA is C.

(A) The animals with the smallest brains spend the most time sleeping. ---> Irrelevant. Nothing has been discussed about duration of sleeping time; only dreams have been discussed.

(B) Immediately after a person awakens from normal sleep, her or his memory contains virtually no accidental associations between ideas. ---> Not necessarily true. Its going to an extreme (virtually no accidental).

(C) When a mammal that would normally dream is prevented from dreaming, the functioning of its memory will be impaired. ---> Very true. The hypothesis states that extra memory space will be required by animals who do not dream in order to ensure that they have an effective memory. In this option, we will not assume that the mammal its talking about has an extra memory space. So, if we apply this hypothesis in general, then option C will be most strongly supported.

(D) Insofar as a persons description of a dream involves meaningful associations between ideas, it is an inaccurate description. ---> Not necessarily true. Its not written that a person can only dream of meaningless, accidental associations between ideas; he might dream something meaningful.

(E) All animals other than the spiny anteater dream. ---> Usage of extreme word (All animals). Excerpt discusses only mammals.



The explanation you have given for D that Person can dream also meaningful then apply to C also. As answer expect strong support for the hypothesis, as per the explanation their is possibility he never dream of meaningless and never get a memory clog.

Although for supporting D in paragraph its mentioned "According to one hypothesis, dreams are produced when the brain is erasing parasitic connections (meaningless, accidental associations between ideas)"

Kindly Elaborate.
2292

Since the deregulation of airlines, delays at the nations increasingly busy airports have increased by 25 percent. To combat this problem, more of the takeoff and landing slots at the busiest airports must be allocated to commercial airlines.
Which of the following, if true, casts the most doubt on the effectiveness of the solution proposed above?

(A) The major causes of delays at the nations busiest airports are bad weather and overtaxed
air traffic control equipment.
(B) Since airline deregulation began, the number of airplanes in operation has increased by
25 percent.
(C) Over 60 percent of the takeoff and landing slots at the nations busiest airports are
reserved for commercial airlines.
(D) After a small Midwestern airport doubled its allocation of takeoff and landing slots, the
number of delays that were reported decreased by 50 percents.
37
(E) Since deregulation the average length of delay at the nations busiest airports has
doubled.


Ans is given (A)...
My concern is that : In question it is clearly mentioned that only after the de-regulation the overcrowding has increased.

Had the overcrowding be due to weather problem, then the same problem would have been present before de-regulation.

2293

One more :-

Many people argue that tobacco advertising plays a crucial role in causing teen-agers to start or continue smoking. In Norway, however, where there has been a ban on tobacco advertising since 1975, smoking is at least as prevalent among teen-agers as it is in countries that do not ban such advertising.

Which of the following statements draws the most reliable conclusion from the information above?
(A) Tobacco advertising cannot be the only factor that affects the prevalence of smoking among teen-agers.
(B) Advertising does not play a role in causing teen-agers to start or continue smoking.
(C) Banning tobacco advertising does not reduce the consumption of tobacco.
(D) More teen-agers smoke if they are not exposed to tobacco advertising than if they are.
(E) Most teen-agers who smoked in 1975 did not stop when the ban on tobacco advertising was implemented.

2294
One more :-

Many people argue that tobacco advertising plays a crucial role in causing teen-agers to start or continue smoking. In Norway, however, where there has been a ban on tobacco advertising since 1975, smoking is at least as prevalent among teen-agers as it is in countries that do not ban such advertising.

Which of the following statements draws the most reliable conclusion from the information above?
(A) Tobacco advertising cannot be the only factor that affects the prevalence of smoking among teen-agers.
(B) Advertising does not play a role in causing teen-agers to start or continue smoking.
(C) Banning tobacco advertising does not reduce the consumption of tobacco.
(D) More teen-agers smoke if they are not exposed to tobacco advertising than if they are.
(E) Most teen-agers who smoked in 1975 did not stop when the ban on tobacco advertising was implemented.

Is A the answer?
2295
Nitin. Says
Is A the answer?


Yes, it is. What is wrong with option B or C ?
2296
The explanation you have given for D that Person can dream also meaningful then apply to C also. As answer expect strong support for the hypothesis, as per the explanation their is possibility he never dream of meaningless and never get a memory clog.

Although for supporting D in paragraph its mentioned "According to one hypothesis, dreams are produced when the brain is erasing parasitic connections (meaningless, accidental associations between ideas)"

Kindly Elaborate.


You're right Nitin. But if you look at the argument closely, it says "the hypothesis predicts that for an animal that did not dream to have an effective memory that animal would need extra memory space for the parasitic connections" and the question asks what the argument "strongly" supports. Although there is mention about the accidental associations in the argument, the argument actually talks more about the memory space getting occupied by these associations.
2297
One more :-

Many people argue that tobacco advertising plays a crucial role in causing teen-agers to start or continue smoking. In Norway, however, where there has been a ban on tobacco advertising since 1975, smoking is at least as prevalent among teen-agers as it is in countries that do not ban such advertising.

Which of the following statements draws the most reliable conclusion from the information above?
(A) Tobacco advertising cannot be the only factor that affects the prevalence of smoking among teen-agers.
(B) Advertising does not play a role in causing teen-agers to start or continue smoking.
(C) Banning tobacco advertising does not reduce the consumption of tobacco.
(D) More teen-agers smoke if they are not exposed to tobacco advertising than if they are.
(E) Most teen-agers who smoked in 1975 did not stop when the ban on tobacco advertising was implemented.


Certainly A
2298
bishoo123 Says
Yes, it is. What is wrong with option B or C ?

Since the figure of number of teenagers who smoke is not given. So, its not possible to compare the effect of advertising merely with the figures of other region.
2299
One more :-

Many people argue that tobacco advertising plays a crucial role in causing teen-agers to start or continue smoking. In Norway, however, where there has been a ban on tobacco advertising since 1975, smoking is at least as prevalent among teen-agers as it is in countries that do not ban such advertising.

Which of the following statements draws the most reliable conclusion from the information above?
(A) Tobacco advertising cannot be the only factor that affects the prevalence of smoking among teen-agers.
(B) Advertising does not play a role in causing teen-agers to start or continue smoking.
(C) Banning tobacco advertising does not reduce the consumption of tobacco.
(D) More teen-agers smoke if they are not exposed to tobacco advertising than if they are.
(E) Most teen-agers who smoked in 1975 did not stop when the ban on tobacco advertising was implemented.

Nitin. Says
Is A the answer?

bishoo123 Says
Yes, it is. What is wrong with option B or C ?


Ya, even i agree the answer is A. now what is wrong with B and C is:
B says: Advertising does not play a role in causing teen-agers to start or continue smoking...
now which advertising are we talking about here? it could be tobacco advertising/soap advertising/drinking advertising/legal advertising/or anything for that matter.fine in the premise we are talking of tobacco advertising but when it comes to answer choices, be very narrow minded.
The point is: you cannot assume that it is only tobacco advertising unless it is mentioned clearly in the answer choice such as A here. that's the beauty of CR answer choices. you do that and fall in trap that Gmat set makers have prepared for you.

and C says: Banning tobacco advertising does not reduce the consumption of tobacco.
It generalizes everything. that takes into account-teenagers, adults, old citizens, infants and anyother group you can think of.
we are only concernced about smoking habits among teen-agers based on the advertising.
so it is eliminated.

Be very careful and narrow minded when considering every CR answer choice.
Hope this clears your doubt.

Regards,
Neha
2300
Since the deregulation of airlines, delays at the nations increasingly busy airports have increased by 25 percent. To combat this problem, more of the takeoff and landing slots at the busiest airports must be allocated to commercial airlines.
Which of the following, if true, casts the most doubt on the effectiveness of the solution proposed above?

(A) The major causes of delays at the nations busiest airports are bad weather and overtaxed
air traffic control equipment.
(B) Since airline deregulation began, the number of airplanes in operation has increased by
25 percent.
(C) Over 60 percent of the takeoff and landing slots at the nations busiest airports are
reserved for commercial airlines.
(D) After a small Midwestern airport doubled its allocation of takeoff and landing slots, the
number of delays that were reported decreased by 50 percents.
37
(E) Since deregulation the average length of delay at the nations busiest airports has
doubled.

Ans is given (A)...
My concern is that : In question it is clearly mentioned that only after the de-regulation the overcrowding has increased.

Had the overcrowding be due to weather problem, then the same problem would have been present before de-regulation.


I like this question, cause no matter how many times i have done it, i always mark the answer wrong but your doubt helped me resolved my doubt too. thankyou for posting the ques and your doubt. will try to clearify your doubt as much as I can.

Dude, your reasoning is very valid and therein lies the answer too.
See- the premise says:
deregulation is already there irrespective of the fact-there is crowding or not. now the ppl concernced, thought that deregulation is by delaying flights so they found a solution that: by shifting flights to commercial airlines will help solve the deregulation problem.

now we are asked to weaken the conclusion. and what's the conclusion, it is: that by shifting flights to commercial airlines will solve the problem. now how can we weaken it?
either by showing that commercial airlines are absolutely busy and there is no scope of diverting flights to commercial airlines or by indicating that there is one major that will not be solved by keeping the flights to the current airlines or by shifting to the commercial airlines.

now the latter one is done A. A states, that the major causes of the delays lies elsewhere, thereby casting doubt on the effectiveness of the proposed solution. and thus is the best answer.

i know, on looking first we say C says that 60% of landing slots in commercial airlines is reserved. but what about the rest 40%? doesn't the rest 40% implies that: atleast some slots are available to be allocated to commercial airlines?
C does imply that so it is eliminated.
if it was given that 100% of the landing slots in commercial airlines is reserved then we would have considered C to weaken the proposed solution. but such is not the case.

Choice B describes another part of the problem, but says nothing about who uses the additional airplanes. Choice D gives one example where allocation was in fact successful, and choice E gives additional information about the scope of the problem.

Hope it clears your doubt.

Regards,
Neha
2301

Folks plz try this problem:

Q.
No nation in the world has experienced as significant a decline in its Yucaipa tree population as our nation. Yet only our nation imposes a law prohibiting the use of Yucaipa tree-bark oil in cosmetics. The purpose of this law in the first place was to help maintain the Yucaipa tree population, at least in this nation. But the law is clearly unnecessary and therefore should be repealed.

Which of the following, if true, would most seriously weaken the conclusion drawn in the passage?



a. This nation contains more Yucaipa trees than any other nation.

b. Yucaipa tree-bark oil is not used for any consumer goods other than cosmetics.

c. The demand for cosmetics containing Yucaipa tree-bark oil is expected to decline in the future in other nations while continuing unabated in this nation.

d. In other countries, labor used to harvest Yucaipa trees for cosmetics is less expensive than comparable labor in this nation.

e. In this nation, some wild animals eat Yucaipa tree bark, thereby contributing to their destruction.

Plz give your supporting explaination.

2302

Plz try this one too->

Q.
Some official Web sites of regionally accredited colleges have received the highest possible rating from the Federal Department of Education. However, all official Web sites of nationally accredited colleges have received the highest possible rating from the same department.

Which of the following, if added to the statements above, would provide most support for the conclusion that all Web sites administered by individuals holding advanced degrees in educational technology have received the highest possible rating from the Federal Department of Education?



a. Only official Web sites of nationally accredited colleges are administered by individuals holding advanced degrees in educational technology.

b. All official Web sites of nationally accredited colleges are administered by individuals holding advanced degrees in educational technology.

c. Only Web sites that have not received the highest possible rating from the Federal Department of Education are administered by individuals not holding advanced degrees in educational technology.

d. All official Web sites of nationally accredited colleges are administered by individuals holding advanced degrees in educational technology.

e. No Web site administered by individuals holding advanced degrees in educational technology is an official Web site of a regionally accredited college.

2303

Is the answer A?
I'll explain if the answer is right.

Folks plz try this problem:

Q.
No nation in the world has experienced as significant a decline in its Yucaipa tree population as our nation. Yet only our nation imposes a law prohibiting the use of Yucaipa tree-bark oil in cosmetics. The purpose of this law in the first place was to help maintain the Yucaipa tree population, at least in this nation. But the law is clearly unnecessary and therefore should be repealed.

Which of the following, if true, would most seriously weaken the conclusion drawn in the passage?


a. This nation contains more Yucaipa trees than any other nation.

b. Yucaipa tree-bark oil is not used for any consumer goods other than cosmetics.

c. The demand for cosmetics containing Yucaipa tree-bark oil is expected to decline in the future in other nations while continuing unabated in this nation.

d. In other countries, labor used to harvest Yucaipa trees for cosmetics is less expensive than comparable labor in this nation.

e. In this nation, some wild animals eat Yucaipa tree bark, thereby contributing to their destruction.

Plz give your supporting explaination.