LSAT Logical Reasoning : Necessary Assumption
Study concepts, example questions & explanations for LSAT Logical Reasoning
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Example Questions
Example Question #1 : Necessary Assumption
Standard sheets of printer paper do not vary in the amount of wood pulp that they contain. Twenty-five percent of the wood pulp contained in a certain class of sheets of standard printer paper (Class B) was recycled from used sheets of standard printer paper of a different class (Class A). Since all Class A sheets were recycled into Class B sheets and since the amount of material other than wood pulp in a sheet of standard printer paper is negligible, it follows that Class B contains 4 times as many sheets of paper as Class A.
The conclusion of the argument follows logically if which one of the following is assumed?
All of the paper in Class A had been made from recycled wood pulp.
The percentage of wood pulp in a sheet of standard printer paper that can be recovered during recycling varies depending on how such paper was used.
When a sheet of standard printer paper is a recycled, all of its wood pulp is recovered.
Class B sheets of paper cannot be recycled further.
Unrecycled wood pulp is of better quality than recycled wood pulp.
When a sheet of standard printer paper is a recycled, all of its wood pulp is recovered.
Since 25 percent of wood pulp in the Class B sheets comes from recycled Class A sheets, the maximum number of Class B sheets is 4 times the number of Class A sheets. However, the correct answer correctly notices that the maximum number of Class B sheets can be produced only if all pulp from the Class A sheets can be recovered through recycling; if less than all of the pulp can be recovered, the actual number of Class B sheets produced will fall short of the maximum. For example, if there were 100 Class A sheets recycled, but only 25 percent of pulp could be recovered through recycling, only 100 Class B sheets could be produced.
Example Question #2 : Necessary Assumption
Soccer players are faster than baseball players because soccer players use more strenuous training programs. Baseball players should use the same training programs as soccer players to become more athletic. More athletic players will be more successful.
Which of the following, if assumed, would allow the conclusion above to be properly drawn?
Baseball requires different skills than soccer
Speed is important to success in baseball
Baseball players do not train very often during the season
Players who become faster become more athletic
Fast baseball players sometimes also play soccer
Players who become faster become more athletic
The argument asserts that different training programs cause soccer players to be faster than baseball players. The next assertion is that baseball players would become more athletic if they used training programs of soccer players. This only follows if becoming faster necessarily makes one more athletic.
Example Question #1 : Determining Which Answer Is An Assumption On Which The Argument Depends
It is important that each driver have an insurance policy before driving on the road. Otherwise, people may not be compensated when they are injured in car accidents. Everyone injured in accidents deserves to be compensated.
The argument assumes which of the following?
If every driver is insured, every person injured in an accident will be compensated
Compensation always requires monetary payment
Those who are injured in accidents are never at fault for those accidents
All car accidents result in injuries
No one who is in an accident but is uninjured deserves to be compensated
If every driver is insured, every person injured in an accident will be compensated
If injured people might not be compensated even if every driver has insurance, then the argument's conclusion does not follow.
Example Question #1 : Determining Which Answer Is An Assumption On Which The Argument Depends
Example Question #1 : Identifying Assumptions
The business model of internet cafes is no longer capable of success in the United States. This is because the availability of internet has skyrocketed over the past several years. Free wifi is offered in most major coffee shops and stores. Additionally, Americans have mobile devices with plans that provide them with internet access. For those without devices, public libraries also provide computers offering internet access, free of charge.
The argument depends on which of the following assumptions?
Internet cafes do not offer any other services, aside from online access, that would enable them to be profitable.
Internet cafes can still be profitable in other countries, just not the United States.
Internet cafes were profitable five years ago.
Public libraries are the only accessible locations where anyone can use the internet.
Major coffee shops are in direct competition with internet cafes.
Internet cafes do not offer any other services, aside from online access, that would enable them to be profitable.
The correct answer is:
Internet cafes do not offer any other services, aside from online access, that would enable them to be profitable.
The crux of the argument is that internet cafes are not successful because the service that they offer -- online access -- is now made available for free by other outlets. However, this argument depends on the assumption that internet cafes do NOT offer any other services that would make them profitable -- such as a community base that would attract clients, or food and beverages that consumers would be interested in buying.
Example Question #3 : Necessary Assumption
A law degree is necessary to practice as an attorney. Further, no one who has demonstrated moral turpitude may be admitted to practice law. Consequently, Smith, who was convicted of embezzlement several years ago, cannot be admitted to practice law.
The argument follows logically if which of the following is assumed?
Smith's conviction is nor revocable.
Embezzlement demonstrates moral turpitude.
Behavior that demonstrates moral turpitude includes the commission of certain crimes.
Embezzlement is a serious crime.
Embezzlement raises issues of integrity which can bar someone from practicing as an attorney.
Embezzlement demonstrates moral turpitude.
To answer this question, it is necessary to realize that the criteria to practice law requires that a person not demonstrate moral turpitude. Therefore, there has to be a link between Smith's embezzlement and the moral turpitude. Therefore, if embezzlement demonstrates moral turpitude, then the argument flows logically.
Example Question #7 : Necessary Assumption
Sports commentator: Miles has received criticism from fans and sportswriters as a second-rate basketball player because he is considered too short and he cannot dribble effectively with his left hand. But this evaluation of Miles’s virtues as a basketball player is unfair, since there have been successful running backs in professional football who are short and who exhibited a strong preference for veering towards the right to evade tacklers.
Which one of the following is an assumption on which the argument depends?
It is unfair to jump to conclusions about athletic prowess and effectiveness simply because a player is short.
Height and left-right preferences have comparable value in football and basketball.
Evaluation of basketball players must take into account what position they play on a team, and in particular, what kind of role a coach assigns to them to effectuate the goals of the team.
Miles’s virtues as a basketball player should be determined by relevant statistics, such as shooting percentage and steals.
Some sports fans do not appreciate how short stature can be advantageous in football and basketball and how quickness can override any handicap arising from preferring the right over the left when moving on a court or field.
Height and left-right preferences have comparable value in football and basketball.
In any assumption question, we must identify what term, concept, or idea is expressed in the evidence that does not appear in the conclusion. In this instance, the evidence concerns football running backs. Therefore, any viable answer choice must refer meaningfully to football. Any answer choice that does not do this should be eliminated. The essence of the argument here involves an assumption that football and basketball are comparable sports. So the correct answer is: Height and left-right preferences have a comparable value in football and basketball.
Example Question #2 : Determining Which Answer Is An Assumption On Which The Argument Depends
It is wrong to condemn the eating of lobster. Lobsters do not have the kind of cognitive abilities that permits meaningful self-awareness, and that sort of cognitive ability is essential to experience suffering.
The conclusion above follows logically if which one of the following is assumed?
Any sentient being that can experience suffering must necessarily have highly developed cognitive abilities.
Only organisms that are self-aware can experience suffering.
If lobsters ought not to be eaten because they can experience suffering, then the same is true with respect to pigs.
Only sentient beings that can experience suffering ought to be considered outside the realm of edible food for humans.
Any sentient beings that can experience suffering deserve to be treated respectfully.
Only sentient beings that can experience suffering ought to be considered outside the realm of edible food for humans.
The assumption must speak to the issue of “experiencing suffering,” since that is the missing term in the conclusion. The correct answer links that new term to the conclusion regarding what humans ought to eat and not eat. Thus, the correct answer is: Only sentient beings that can experience suffering ought to be considered outside the realm of edible food for humans.
Example Question #9 : Necessary Assumption
Outlining a story's plotline before actually drafting the story reduces the amount of writing time. But writing a story through free-writing to generate a first draft, which then can be reformulated through rigorous editing, produces a more creative narration of events. Therefore, when quality fiction writing is more important than generating a quick writing product, outlining should give way to free-writing.
Which one of the following is an assumption required by the argument?
Writing is never improved through outlining or other time-saving strategies.
Creative narration of events in a story enhances the quality of fiction writing.
Fiction writing is a painstaking process that cannot be made easier through outlining.
Free-writing is best used in fiction writing, but its value in expository writing is suspect.
The more creative the storytelling, the better the finished product, at least when it comes to fiction.
Creative narration of events in a story enhances the quality of fiction writing.
The conclusion speaks of free-writing as better than outlining when it comes to generating quality fiction. The premise (i.e., the evidence) for that conclusion speaks of "creative narration of events." That idea does not appear in the conclusion, so in order to link the premise to the conclusion, the assumption must address it in some meaningful way. The correct answer here does just that, by linking the idea of "creative narration of events" and the point in the conclusion about quality fiction.
Example Question #4 : Necessary Assumption
The company now only hires persons with a post-graduate degree. Further, the company prefers to hire employees with significant work experience. Performance evaluations over the years have shown, however, that new hires with significant work experience outperform those without such experience, regardless of education level. Therefore, if the company relaxes the degree requirement and makes significant work experience mandatory, overall employee performance among new hires should increase.
Which one of the following is an assumption that would allow the conclusion above to be properly drawn?
Some new hires at the company have previously included persons who have a post-graduate degree, but no significant work experience.
All performance evaluations by the company are done fairly and accurately.
Some persons with post-graduate degrees have been unable to gain significant work experience while completing their studies.
New hires are evaluated by the company every six months to determine their employee performance.
The company's hiring policy has been in place long enough to determine its long-term effects.
Some new hires at the company have previously included persons who have a post-graduate degree, but no significant work experience.
The correct answer is an unstated premise necessary to the argument’s conclusion, which is that “overall employee performance among new hires should increase.” Without this premise, it is possible that new hires’ performance will merely remain the same, as the company’s new hires may have all had significant work experience (despite it being a preference and not a requirement).
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