Summary
Today, we’re learning about glass. Glass is a fluid, so when it’s put under pressure, its volume stays the same but it flows slowly to an area of lesser pressure. The stimulus proposes an example where an extremely heavy object is placed on the middle of a sheet of glass. So what happens?
Strongly Supported Conclusions
Based on the scenario given, we can see that a heavy object would put pressure on the middle of the sheet of glass. Because glass flows away from pressure without changing in volume, we can infer that over time the sheet of glass would shift away from the pressure, becoming thinner in the middle where the object is, and thicker around the edges.
A
become larger in size yet still be of uniform thickness
This is anti-supported. Because fluid flows away from areas of higher pressure, the glass would thin out in the part under the heavy object and become thicker in the non-pressured areas. Thus, it would not remain uniformly thick.
B
flow toward the point at which the pressure of the object is greatest
This is anti-supported. The stimulus directly states that fluids flow away from areas of higher pressure. Since glass is a fluid, it would therefore flow away from the point of greatest pressure, not towards.
C
compress, although not as much as a piece of steel would
This is anti-supported. The stimulus explains that glass, as a fluid, does not compress; instead, it flows. Because fluids do not compress, glass would not compress under pressure.
D
divide into exactly two pieces that are equal in neither size nor shape to the original piece of glass
This is not supported. The stimulus specifically sets out the condition that the glass would not crack, so it could only divide into two pieces if the glass flowed fully out from underneath the object. And we just don’t have a good sense of whether or not that would happen.
E
be thinner in the portion of the glass that is under the pressure of the object than in those portions of the glass that are not under that pressure
This is strongly supported. We know that glass flows away from pressure. This means it would slowly move away from the pressure created by the object and towards non-pressured areas, causing the sheet to be thinner where there’s pressure and thicker where there isn’t.
Summary
Despite what some anthropologists claim, agriculture must not have begun under conditions of drought and hunger. Why? Because agricultural discoveries are the result of the study of natural processes. People cannot study natural processes without leisure, and people have leisure only when resources are plentiful.
Strongly Supported Conclusions
Agriculture began under societies that had plentiful resources.
A
whenever a society has plentiful resources, some members of that society devote themselves to the study of natural processes
Plentiful resources are a necessary condition for people to devote themselves to studying natural processes. We don’t know whether a sufficient condition occurs just because a necessary condition occurs.
B
plants cannot be cultivated by someone lacking theoretical knowledge of the principles of plant generation and growth
We don’t know whether plants cannot be cultivated if a person lacks theoretical knowledge. The stimulus also does not address what would be considered theoretical knowledge.
C
agriculture first began in societies that at some time in their history had plentiful resources
Since some anthropologists are wrong, agriculture must have begun when a society had plentiful resources.
D
early agricultural societies knew more about the natural sciences than did early nonagricultural societies
We don’t know anything about nonagricultural societies. Additionally, the stimulus is limited to agriculture, whereas “natural sciences” is too broad.
E
early societies could have discovered by accident how the plants they cultivated reproduced and grew
We don’t know whether early societies discovered agriculture by accident.
Summary
The percent of money spent on treating disease X that went to standard (effective) treatments has gone down over the past 10 years. Thus, the amount of money spent on effective treatments of disease X has gone down over the past 10 years.
Missing Connection
Although the PERCENT that went to standard treatments has gone down, that doesn’t prove anything about the AMOUNT spent on standard treatments. This is because the overall amount spent on treating disease X might have increased. To prove that the amount spent on standard treatments has gone down, we want to learn that the overall amount spent on treating disease X has NOT increased.
A
Varieties of disease X requiring expensive special treatment have become less common during the past decade.
Although these varieties have become less common, that doesn’t prove with certainty that the overall amount spent on treating disease X has not increased. Perhaps these varieties are less common, but people have become more aware of disease X and are more likely to seek treatment for it today.
B
Nonstandard methods of treating disease X are more expensive now than they were a decade ago.
(B) doesn’t establish anything about the overall amount spent on treating disease X. It leaves open the possibility that the overall amount increased, in which case the conclusion wouldn’t have to be true.
C
Of total medical expenditures, the percentage that is due to treatment of disease X increased during the past decade.
We care about whether the overall amount spent on disease X has increased. But the proportion that disease X spending represents out of all medical expenditures (including things such as heart surgery, cancer, etc.) doesn’t reveal anything about the overall amount spent on disease X.
D
Most of the money spent on treating disease X during the last decade went to pay for nonstandard treatments.
Even if most disease X spending goes toward nonstandard treatments, and only, let’s say, 40% goes toward standard treatments, we still don’t know whether overall spending on disease X has increased. So (D) doesn’t guarantee that the amount spent on standard treatments for disease X has gone down.
E
The total amount of money spent on treating disease X slowly declined during the past decade.
(E) establishes that the overall amount of disease X spending has not increased. If we know that the overall amount has not increased, but the % that went to standard treatments has gone down, we can validly infer that the amount that went to standard treatments has gone down.
Motorcoach driver: Professional drivers spend much more time driving, on average, than do other people and hence are more competent drivers than are other, less experienced drivers. Therefore, the speed limit on major highways should not be reduced, because that action would have the undesirable effect of forcing some people who are now both law-abiding and competent drivers to break the law.
Police officer: All drivers can drive within the legal speed limit if they wish, so it is not true to say that reducing the speed limit would be the cause of such illegal behavior.
Speaker 1 Summary
The motorcoach driver claims that we shouldn’t reduce highway speed limits. Why not? Because doing so would “force” some competent drivers to break the law, presumably by speeding. Who would these drivers be? We can infer the motorcoach driver is talking about professional drivers, who are better-than-average drivers because they spend more time driving. (The assumption is that the professionals wouldn’t reduce their speed to respect a new limit.)
Speaker 2 Summary
The police officer argues that lowering the speed limit would not actually be the cause of people speeding. This is because anyone can drive at the limit if they choose to—so the drivers’ choices, not the limit, would be to blame for speeding.
Objective
We need to find a point of disagreement. The driver and the officer disagree about whether lowering the speed limit would cause any drivers to speed.
A
it would be desirable to reduce the speed limit on major highways
The motorcoach driver disagrees with this, but the police officer doesn’t state an opinion. The police officer never mentions whether or not we should change the speed limit.
B
professional drivers will drive within the legal speed limit if that limit is reduced
The motorcoach driver disagrees with this, but the police officer neither agrees nor disagrees. The police officer doesn’t say whether professional drivers actually will speed; the point is just that if they did so it would be their own fault.
C
reducing the speed limit on major highways would cause some professional drivers to break the law
The motorcoach driver agrees with this, but the police officer disagrees, so this is the point at issue. The police officer claims that the cause of speeding would not be the lower limit, but would instead be that the drivers chose to speed.
D
professional drivers are more competent drivers than are other, less experienced drivers
The motorcoach driver agrees with this, but the police officer doesn’t state an opinion. The police officer doesn’t say anything at all about the competency of professional versus non-professional drivers.
E
all drivers wish to drive within the speed limit
Neither speaker states an opinion about this claim. Neither the motorcoach driver nor the police officer makes any kind of statement about what drivers actually wish to do.
Summary
The argument concludes that a certain near-extinct rhinoceros species could be saved by regularly trimming the horns of all rhinos. How would this help? Because the reason that the species is endangered is because of poachers trading in rhino horns, and trimming the horns would remove the motivation for poaching.
Notable Assumptions
The argument assumes that resolving the cause that initially led to this species becoming endangered would be enough to allow the species’ survival going forward. In other words, the species hasn’t reached a point where even eliminating poaching won’t save it.
The argument also assumes that trimming the rhinos’ horns wouldn’t have unexpected consequences that could further endanger the species, such as making the rhinos more vulnerable to predators or lowering their reproductive rate.
The argument also assumes that trimming the rhinos’ horns wouldn’t have unexpected consequences that could further endanger the species, such as making the rhinos more vulnerable to predators or lowering their reproductive rate.
A
Most poachers who are discouraged from hunting rhinoceroses are not likely to hunt other animals for their horns.
The argument is only concerned with ensuring the survival of this rhino species, so it’s not necessary that other animals will not become endangered.
B
At least some rhinoceroses whose horns are periodically trimmed off will be able to attract mates.
In order for the rhino species to survive, the members of the species must be able to reproduce. If trimming their horns totally prevented the rhinos from finding mates, they would go extinct even without poachers. That’s why this assumption is necessary.
C
Poachers hunt at least some immature rhinoceroses whose horns have not yet started to develop.
Ensuring the species’ survival doesn’t require protecting every single member of the species from hunting, so this assumption isn’t necessary.
D
The demand for rhinoceros horns will remain constant even if the supply decreases after the periodic trimming-off of the rhinoceros horns has begun.
Whatever happens to the demand for rhino horns is irrelevant, especially given the premise that trimming rhino horns would eliminate the motivation to continue poaching.
E
Rhinoceroses whose horns have been trimmed off are unable to defend themselves against predators.
Far from being necessary, this assumption would undermine the argument. In fact, it’s the exact opposite of one possible necessary assumption: that rhinos with trimmed horns would be able to defend themselves.