LSAT Logical Reasoning : Determining which answer must be true based on the information given

Study concepts, example questions & explanations for LSAT Logical Reasoning

varsity tutors app store varsity tutors android store

Example Questions

Example Question #11 : Lsat Logical Reasoning

If an artist is fully motivated to succeed, he or she will create inspirational works of art.  However, a work of art cannot be inspirational unless it comes from the depths of the artist’s soul.  When art is based upon the chief passions or desires of the artist, then – and only then – it comes from the depths of the artist’s soul.

If all of the above statements are true, which one of the following must also be true?

Possible Answers:

If an artist creates no art based upon his or her chief passions or desires, he or she is not fully motivated to succeed.

A work of art will likely be inspirational unless it is not based upon the chief passions or desires of the artist.

Any art that is based upon an artist’s chief passions or desires is inspirational.

If a work of art comes from the depths of the artist’s soul, it is inspirational unless the artist is not fully motivated to succeed.

If an artist does not create inspirational works of art which come from the depths of the artist’s soul, the artist cannot be successful.

Correct answer:

If an artist creates no art based upon his or her chief passions or desires, he or she is not fully motivated to succeed.

Explanation:

The correct answer choice is the only one that is logically sound.  If the artist creates no art based upon chief passions or desires, the art does not come from the depths of the artist’s soul, and thus it cannot be inspirational.  This, of course, means that the artist cannot be fully motivated to succeed, because if he or she were, the works of art would be inspirational.  The incorrect answer choices mistake necessary conditions for sufficient conditions and thus are not logically sound.

Example Question #11 : Lsat Logical Reasoning

Most standardized tests can only be mastered by studying prior test administrations.  Though studying the abstract principles and concepts likely to be tested can improve a student’s score, there is no substitute for actual, concrete problems to get inside the minds of the test-makers.  Indeed, if one studies a sufficient amount of prior tests, one will find that the very same problems are often repeated with minimal alterations.

The statements above, if true, most strongly support which one of the following?

Possible Answers:

At least some students taking standardized tests must study actual, concrete problems to master the tests.

A student need not study abstract principles or concepts to master standardized tests.

If a student studies a sufficient amount of prior tests, he or she will master the standardized test being taken.

Students must get inside the minds of the test-makers in order to achieve high scores on standardized tests.

Most standardized tests contain problems which are very similar to those given on prior administrations of the tests.

Correct answer:

At least some students taking standardized tests must study actual, concrete problems to master the tests.

Explanation:

Because the statements indicate that most (not all) standardized tests can be mastered by studying prior test administrations with actual concrete problems, at least some students will need to do so to master those tests.  The other answer choices either go too far in their inferences or misstate the premises given.

Example Question #11 : Lsat Logical Reasoning

Most fast food restaurants are inexpensive restaurants, and most fast food restaurants serve unhealthy food.  Additionally, all restaurants that serve unhealthy food provide poor service.  Most restaurants that provide poor service are disliked by the general public.

Assuming the statements above are true, which one of the following can be properly inferred?

Possible Answers:

Most restaurants that are disliked by the general public are inexpensive restaurants.

All fast food restaurants that serve unhealthy food are disliked by the general public.

Some restaurants are both inexpensive and provide poor service.

Most fast food restaurants are disliked by the general public.

Some restaurants that provide good service are liked by the general public.

Correct answer:

Some restaurants are both inexpensive and provide poor service.

Explanation:

Because we know that most fast food restaurants are both inexpensive and serve unhealthy food, at least some of the restaurants fall into both categories.  Since all restaurants that serve unhealthy food also provide poor service, it can be concluded that some restaurants are both inexpensive and provide poor service.  The remaining answer choices, while they may be true, are not necessarily true, and thus are incorrect.

Example Question #11 : Inference

A football player cannot be an All-American without both superior athletic talent and an unusual work ethic.  Most football players have an unusual work ethic.  However, most people with superior athletic talent do not play football, but rather other sports such as basketball.  Most basketball players with superior athletic talent do not have an unusual work ethic.

If the statements above are true, which one of the following statements must also be true?

Possible Answers:

Most basketball players with superior athletic talent, if they played football, could not be All-Americans.

Most football players with superior athletic talent could be All-Americans.

At least some basketball players with an unusual work ethic could be All-Americans if they played football.

Most football players could not be All-Americans.

At least some All-American football players also play basketball.

Correct answer:

Most basketball players with superior athletic talent, if they played football, could not be All-Americans.

Explanation:

The passage specifically states two necessary conditions for being an All-American in football: 1) superior athletic talent, and 2) an unusual work ethic.  Because the passage notes that most basketball players who have (1) lack (2), it logically follows that most basketball players could not qualify as All-Americans in football, under the conditions stated.  Note that the passage does not state the conditions sufficient to become an All-American football player; it merely states some necessary conditions.  Nor does the passage tell us anything that would allow drawing a conclusion regarding “most football players” or “at least some All-American football players.”

Example Question #11 : Must Be True

Most students whose standardized test scores are high enough to warrant admission at a prestigious college also have a high grade point average.  However, many students whose grade point average is high do not score high enough on standardized tests to warrant admission at a prestigious college.  Some of these students, however, make up for the score deficiency by participating in extracurricular activities which the prestigious college values; colleges may accept slightly lower scores than normal if this is the case.

If the above statements are true, which one of the following statements must be true?

Possible Answers:

At least some students with a low grade point average do not score enough on standardized tests to warrant admission at a prestigious college.

At least some students whose standardized test scores warrant admission at a prestigious college also participate in extracurricular activities which the prestigious college values.

At least some students with a high grade point average obtained standardized test scores which are high enough to warrant admission at a prestigious college.

Most students with a high grade point average do not need to participate in extracurricular activities to warrant admission at a prestigious college.

Most students who make up for their standardized test score deficiency by participating in extracurricular activities also have a high grade point average.

Correct answer:

At least some students with a high grade point average obtained standardized test scores which are high enough to warrant admission at a prestigious college.

Explanation:

If most students with high standardized test scores also have a high GPA, it must be true that at least some students with a high GPA also have high standardized test scores.  The remaining answer choices, while they may be true, do not have to be true based on the statements in the passage.  The passage does not tell us if students with high standardized test scores participate in extracurriculars, nor do we learn anything about students with low GPAs.

Example Question #12 : Lsat Logical Reasoning

The anonymous administrator said the University will not tolerate any more "social clubs." Violence, drunkenness, and hatred do not represent and have never represented this institution. Secret meetings that promote such activities will be found out and eliminated by the school's administration.

Based on the above, which of the following statements must be true?

Possible Answers:

The University has extremely broad powers in banning student activities.

The University administration does not want any of its students drinking alcohol.

"Social clubs" have created many problems for the University.

The administration is reacting to a specific event rather than to a series of issues.

The University has a vibrant social life, with a variety of groups and clubs.

Correct answer:

"Social clubs" have created many problems for the University.

Explanation:

The "anonymous administrator" only brings up one kind of group at the University, the "social clubs," and cites a pattern of problematic behavior, if obliquely, that is now being dealt with by the administration. Any statements beyond those facts require reading too much into the passage, thus the only statement that can be true is that the "social clubs" have become a serious issue.

Example Question #11 : Must Be True

Athletes work extremely hard to reach the elite level, which by necessity most never will. Their work, effort, and determination is usually extreme, but they are nonetheless viewed quite widely as failures.

Which one of the following statements can be inferred from the passage?

Possible Answers:

The amount of work an athlete puts in has no bearing on their ultimate success.

Only a handful of athletes can be considered elite at any one time.

Many athletes do not show much determination to reach the top.

The athletes that are successful have had advantages such as wealth and opportunity.

Work, effort, and determination are personality traits that cannot be taught.

Correct answer:

Only a handful of athletes can be considered elite at any one time.

Explanation:

The passage notes that very, very few athletes ever succeed, no matter what they do in terms of effort and work. This indicates that there are a limited number of people who could truly be considered "elite" at any one time among athletes, and that they are set apart by something other than hard work, effort, and determination.

Example Question #11 : Determining Which Answer Must Be True Based On The Information Given

Public relations is usually not a service sought out by celebrities until they need it. While the scandal-ridden are certainly most desirous of someone smoothing out their issues with the press, their scandals might have never happened had they had a P. R. professional in the first place.

Which of the following statements most obviously follows from the passage’s logic?

Possible Answers:

Public relations work is only a necessity for a scandal-ridden celebrity.

A celebrity is not able to keep a career going after a serious scandal.

All celebrities will at some point have to deal with a scandal.

The most important element of being a successful public relations professional is finding a scandal-ridden client.

A public relations professional can help some celebrities avoid potential scandals.

Correct answer:

A public relations professional can help some celebrities avoid potential scandals.

Explanation:

The passage explicitly states that any scandal-ridden celebrity would have been better served by having a public relations professional in place well before a scandal had even taken place. This quite clearly suggests that P. R. work is able to minimize the effect of a scandal if it is already in place.

Example Question #11 : Inference

Jen is throwing a party and trying to decide who to invite. Some of her friends do not get along.  She knows she will invite Ben, Nick, or Alice, but not all three of them.  If she invites Nick, she will also invite Alice.

If the statements above are all true, which of the following must also be true?

Possible Answers:

Jen will not invite Nick.

If Jen invites Ben, then she will also invite Alice.

Jen will invite Ben.

Jen will invite only one of the three guests to the party.

If Jen invites Ben, then she will not invite Nick.

Correct answer:

If Jen invites Ben, then she will not invite Nick.

Explanation:

If Jen invites Nick, she must also invite Alice.  If that is the case, Ben cannot be invited because the conditions state that Jen does not invite all three guests. Thus, it must be true that if Jen invites Ben, she will not invite Nick, because if she did, she would have to invite Alice as well and then all three guests would be invited, violating the conditions of the statement.

Example Question #11 : Must Be True

Observation of small groups in workplace environments has revealed important clues as to how leadership gets defined in offices. The person with the most experience or knowledge of the project does not automatically get thrust into a leadership position, but instead has to frequently take a backseat to the person who is loudest and most forceful in directing the actions of others.

Which of the following statements must be true based on the argument presented in the passage?

Possible Answers:

Leaders in workplace situations work differently than leaders in other areas.

A workplace situation is not an ideal environment in which to study leadership abilities.

Workplace leadership is not easy to identify or comment on as a definable characteristic.

Leadership qualities are directly tied to experience and knowledge.

The most experienced and knowledgeable people do not always assert themselves as leaders.

Correct answer:

The most experienced and knowledgeable people do not always assert themselves as leaders.

Explanation:

The passage states that leadership in a workplace environment is not based on anything except for an assertion of authority on the part of people who become leaders. Specifically, the passage notes people with knowledge and experience are not leaders. This means that it can be assumed that those with knowledge and experience do not always assert themselves as leaders.

Learning Tools by Varsity Tutors