Examkin

Logical Reasoning

666 questions

All types666Multiple choice343Multiple select54True / False70Matching166Ordering18Fill in the blank10Short answer5
Question 161Question →

Match each of the following municipal policy decisions to the general administrative principle that most directly justifies it:

Click a left item, then click its matching right item

Items

A municipal transit district reallocated bus routes from an affluent commuter corridor with declining ridership to an underserved industrial district, despite commuter objections regarding diminished convenience, because the industrial route enabled shift workers to maintain essential employment.
A city water utility declined to repair a fractured supply pipe connecting a commercial residential complex to the central main, requiring the property management company to bear the full cost, because the rupture occurred on the customer side of the primary distribution meter.
A public library network replaced its overdue return monetary penalties with a temporary borrowing suspension, despite forfeiting significant operational revenue, because financial penalties disproportionately discouraged low-income patrons from continuing to use library resources.

Matches

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Answer

Transit route reallocation correctly pairs with prioritizing essential economic access over discretionary convenience; Private pipe repair refusal correctly pairs with restricting public funding to infrastructure within municipal boundaries; Library fine elimination correctly pairs with modifying administrative penalties that undermine public access goals.
Each scenario is justified by a principle whose scope and conditional force precisely warrant the specific trade-off enacted: economic necessity over convenience for transit, jurisdictional/property boundaries for utility expenditures, and mission alignment over revenue preservation for public libraries.

Step-by-Step Solution

1
Analyze the factual rationale of each municipal scenario.
Identified the operative rationale in each case: essential employment access over convenience (transit), demarcation of legal/metered property boundaries (water utility), and removing barriers that deter institutional access (library).
Principle questions require extracting the underlying normative rule that bridges the specific action to its justification.
2
Evaluate the normative scope and conditions of the candidate principles.
Matched each specific rule to the corresponding decision without overextending conditional logic or confusing necessary and sufficient conditions.
A valid governing principle must be neither broader than supported by the facts nor logically reversed.
3
Verify pair alignment across all three matches.
Established one-to-one correspondence between every administrative action and its governing normative standard.
Ensures complete structural coherence across the matching set.

Key Concept

Identifying and applying governing normative principles to specific administrative actions
Estimated Time:1m 30s
Question 162Question →

Economist: Some regulators propose banning dynamic pricing algorithms in the airline industry, arguing that these systems implicitly facilitate collusion. This proposed ban is misguided. It is true that these algorithms sometimes independently converge on supra-competitive prices. However, a ban would also eliminate their capacity to instantaneously adjust to fluctuating fuel costs, a feature that significantly lowers fares for off-peak travelers. Ultimately, eliminating this efficiency would cause average ticket prices to rise, thereby harming the very consumers the regulators wish to protect.

Which of the following most accurately describes the role played in the economist's argument by the statement that these algorithms sometimes independently converge on supra-competitive prices?

Show answer & explanation

Answer: It is a concession of a fact that lends support to the regulatory policy the argument as a whole is designed to refute.

Answer

The statement acts as a concession of a fact that lends support to the regulatory policy the argument as a whole is designed to refute.
The correct answer accurately captures that the target statement is an acknowledgment of a negative consequence of algorithmic pricing (converging on high prices). Because it is a negative consequence, it serves as a point in favor of the regulators' proposal to ban the algorithms. The economist's entire argument is structured to refute that specific regulatory proposal.

Step-by-Step Solution

1
Identify the main conclusion of the argument.
The main conclusion is that the regulators' proposed ban on dynamic pricing algorithms is misguided.
This is the central point the economist is trying to prove using the subsequent evidence about fuel costs and consumer harm.
2
Analyze the context immediately surrounding the target statement.
The target statement ('It is true that these algorithms sometimes independently converge on supra-competitive prices') immediately follows the main conclusion and is introduced with 'It is true that...'
Understanding structural indicators like 'It is true that...' helps identify concessions or acknowledgments of opposing views.
3
Determine the logical relationship between the target statement and the main conclusion.
The target statement points out a flaw in algorithms (high prices). This flaw supports the regulators' ban. Since the economist is arguing *against* the ban, this statement goes against the economist's own conclusion.
Mapping the argumentative direction (pro-ban vs. anti-ban) reveals the structural role of the claim.
4
Synthesize the findings into an abstract description of the statement's role.
The statement is a conceded fact that supports the opponent's view (the regulatory policy), which the overall argument attempts to defeat.
Matching the concrete relationship to the abstract language used in LSAT answer choices is required to find the correct option.

Key Concept

Identifying concessions and tracking argumentative direction in multi-perspective stimuli.
Question 163Question →

Analyze the cognitive scientist's argument below. To make the conclusion logically valid, you must supply the missing conditional premise. Fill in the blanks using the exact terminology from the argument to construct the precise sufficient assumption.

Fill in the blanks below

Cognitive Scientist: A computational system possesses genuine semantic understanding only if it can ground its internal symbols in sensorimotor interactions with a physical environment. Because large language models are trained purely by mapping statistical relationships between text tokens, they completely lack sensorimotor engagement with the physical world. Therefore, it is clear that any system incapable of causal reasoning cannot possess genuine semantic understanding.

Missing Premise: A computational system is able to ground its internal in sensorimotor interactions only if it is capable of .
Show answer & explanation

Answer

symbols, causal, reasoning
The correct answer successfully bridges the strict logical gap between the first premise and the conclusion while avoiding the decoy premise about large language models. The argument's core premise is GSU -> G (Genuine Semantic Understanding requires Grounding symbols). The conclusion asserts ~CR -> ~GSU (Lack of Causal Reasoning guarantees lack of Genuine Semantic Understanding). To validate this conclusion, we must establish that ~CR guarantees ~G. The contrapositive of this required assumption is G -> CR (Grounding symbols requires Causal Reasoning). The fill-in-the-blank sentence is structured as 'G only if CR', exactly mirroring this required sufficient assumption. Using the exact text terms yields 'symbols', 'causal', and 'reasoning'.

Step-by-Step Solution

1
Map the formal logic of the core premise.
Genuine Semantic Understanding (GSU) -> Grounds symbols in sensorimotor interactions (G).
The phrase 'only if' introduces a necessary condition.
2
Map the formal logic of the conclusion.
No Causal Reasoning (~CR) -> No Genuine Semantic Understanding (~GSU).
This is the final claim the argument attempts to prove.
3
Identify and isolate the decoy premise.
Large Language Model (LLM) -> No sensorimotor engagement (~G).
This premise shares a term (~G) with the main conditional chain but introduces a specific subject (LLMs) that does not appear in the generalized conclusion.
4
Determine the required deductive gap.
We must prove ~CR -> ~GSU. We know from Step 1 that ~G -> ~GSU (contrapositive). Therefore, we need an assumption establishing that ~CR -> ~G.
Linking the dangling term in the conclusion (~CR) to the necessary condition of the first premise (~G) forms a valid chain: ~CR -> ~G -> ~GSU.
5
Contrapose the required assumption to match the fill-in-the-blank structure.
The assumption ~CR -> ~G is logically equivalent to G -> CR (Grounding symbols requires Causal Reasoning).
The provided sentence template 'A system is able to ground its internal... only if it is capable of...' represents the G -> CR structure.

Key Concept

Formal deduction involving contrapositives and the circumvention of decoy premises in conditional logic chains.
Estimated Time:2m 30s
Question 164Question →

Match each of the following financial regulatory determinations regarding automated lending systems to the general administrative principle that most directly justifies it:

Click a left item, then click its matching right item

Items

A regional credit union was prohibited from deploying an automated credit-scoring model that incorporated zip-code-level demographic proxies, even though the model demonstrably maximized overall loan repayment rates.
A mortgage lender was required to grant manual underwriting appeals exclusively to loan applicants whose automated rejections were triggered by unverified anomalies in secondary financial records.
A digital micro-lender was permitted to use proprietary machine-learning algorithms to determine interest rates without releasing its source code, provided that the exact statistical weight of every applicant variable was made public.

Matches

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Answer

The credit union scenario matches the principle barring demographic proxies despite aggregate performance; the mortgage lender scenario matches the principle mandating individual review for uncorroborated adverse records; the digital micro-lender scenario matches the principle that disclosing criteria weights suffices for accountability without proprietary code release.
Each regulatory determination is paired with the principle whose conditional requirements and normative scope exactly match the facts: demographic proxy prohibition matches the rule against generalized demographic risk assessment; manual review for uncorroborated records matches the rule mandating review for unverified adverse data; and publishing variable weights without source code matches the rule defining sufficient disclosure for algorithmic accountability.

Step-by-Step Solution

1
Analyze the core legal/administrative justification in each scenario
Identified the primary operative tension in each: demographic proxy usage vs. repayment performance in the first; adverse decision based on unverified anomaly vs. appeal rights in the second; source code secrecy vs. variable weighting disclosure in the third.
Principle-matching questions require isolating the exact normative trigger and resulting mandate in each specific factual case.
2
Map each scenario to the governing normative rule that bridges its specific facts to its regulatory outcome
Each scenario maps uniquely to one principle without requiring unwarranted factual assumptions or conditional reversals.
A correctly applied principle must be sufficient to validate the action taken under the specified circumstances.

Key Concept

Principle Identification and Application
Estimated Time:1m 30s
Question 165Question →

Ethologist: In social marine mammals, juvenile play behavior occurs almost exclusively when individuals feel secure. Researchers recently observed that a captive group of juvenile dolphins engaged in complex acrobatic play sequences only during periods when ambient noise from nearby harbor construction dropped below 55 decibels. We can conclude, therefore, that maintaining ambient underwater noise below 55 decibels is sufficient to guarantee that these dolphins will engage in acrobatic play.

The ethologist's reasoning is most vulnerable to criticism on the grounds that it does which one of the following?

Show answer & explanation

Answer: treats a condition that is required for a particular behavior to occur as one that is sufficient to guarantee its occurrence

Answer

The argument's reasoning is flawed because it treats a condition that is necessary for the occurrence of acrobatic play as if it were sufficient to ensure that the behavior will occur.
The argument establishes that ambient noise dropping below 55 decibels was a required circumstance ('only during periods when') for acrobatic play to occur. From this observation, the author concludes that establishing this condition will guarantee ('is sufficient to guarantee') that play will occur. This is a classic conditional reversal error, mistaking a necessary condition for a sufficient one.

Step-by-Step Solution

1
Analyze the structural premises and conditional indicators in the stimulus.
The premise states that juvenile dolphins engaged in acrobatic play 'only during periods when' noise was below 55 dB, meaning Noise < 55 dB is a necessary condition for play (Play → Noise < 55 dB).
Identifying necessary vs. sufficient indicator terms is essential for evaluating formal conditional deductions.
2
Analyze the argument's conclusion.
The conclusion claims that maintaining noise below 55 dB is 'sufficient to guarantee' that the dolphins will engage in acrobatic play (Noise < 55 dB → Play).
Comparing the conclusion to the premises determines whether the logical inference is valid or fallacious.
3
Isolate the logical disconnect and match with the correct abstract flaw description.
The author commits a conditional reversal (confusion of necessity and sufficiency) by treating an essential prerequisite as a guaranteed trigger.
The correct response must accurately state this specific structural vulnerability without introducing outside assumptions.

Key Concept

Conditional Reversal (Mistaking a Necessary Condition for a Sufficient Condition)
Estimated Time:1m 30s
Question 166Question →

Match each of the following institutional scenarios (Left) to the abstract normative principle (Right) that most strictly governs and justifies the logical reasoning applied in the scenario.

Click a left item, then click its matching right item

Items

The Heritage Trust recently withdrew a historically significant tapestry from its viewing gallery, sealing it in a dark, climate-controlled vault to halt light degradation. This maneuver was entirely justified, considering that the Trust's substantial financial endowment ensures that public admission fees are not necessary to subsidize the tapestry's ongoing conservation.
The Continental Museum determined that a ceremonial sword in its collection was originally seized by an imperial general under direct threat of violence. Nevertheless, the museum rightfully denied a formal petition to return the sword to its nation of origin, citing an ongoing armed conflict in that territory which guarantees the artifact would be immediately smelted for scrap metal upon arrival.
The State Archive recently redacted the names of key informants in a declassified 1960s surveillance ledger. This redaction was fundamentally improper. Although the informants remain alive and explicitly requested privacy, eliminating their identities renders scholars completely unable to reconstruct the true structural biases of the decade's intelligence operations.
The Royal Gallery plans to exhibit statues that were looted during a colonial occupation. Because the gallery will install extensive placards detailing the violent reality of the acquisition, and because the descendants of the original creators have merely staged public protests rather than initiating formal legal proceedings to reclaim the statues, the exhibition is ethically permissible.

Matches

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Answer

Tapestry matches Conservation Principle; Sword matches Repatriation Principle; Archive matches Redaction Principle; Statues matches Exhibition Principle.
Each scenario perfectly traces the conditional logic of its corresponding principle. The Tapestry scenario utilizes a biconditional rule regarding conservation funding. The Sword scenario triggers a conditional duty but immediately applies its specific override. The Archive scenario concludes an action is improper by showing a necessary condition (historical integrity) was not met. The Statues scenario concludes an action is permissible by satisfying a sufficient condition while avoiding the disqualifying proviso.

Step-by-Step Solution

1
Analyze the logical structure of the Tapestry scenario.
Identified a justification based on funding independence.
This uniquely maps to the Conservation Principle's biconditional requirement regarding financial revenue.
2
Analyze the logical structure of the Sword scenario.
Identified a duty established by violence but overridden by imminent destruction.
This precisely maps to the conditional override in the Repatriation Principle.
3
Analyze the logical structure of the Archive scenario.
Identified an action deemed improper because it degrades historical understanding, despite meeting a privacy condition.
This is an application of the contrapositive (modus tollens) of the Redaction Principle's necessary condition.
4
Analyze the logical structure of the Statues scenario.
Identified an action deemed permissible because context is provided and active litigation is absent.
This satisfies the sufficient condition and proviso outlined in the Exhibition Principle.

Key Concept

Applying complex conditional logic, exceptions, and contrapositives to specific scenarios.
Estimated Time:3m 0s
Question 167Question →

Carefully analyze the four arguments presented on the left. Match each stimulus to the abstract description on the right that most accurately identifies its pattern of reasoning or its logical flaw.

Click a left item, then click its matching right item

Items

If a medieval codex features both lapis lazuli illumination and a calfskin binding, its provenance can be definitively traced to the Saint-Martin scriptorium. The newly recovered Codex Aureus cannot be traced to the Saint-Martin scriptorium. Hence, the Codex Aureus must lack either lapis lazuli illumination or a calfskin binding.
Survival in the extreme pressure of the Mariana Trench abyss requires an organism to synthesize piezolyte proteins. The recently discovered amphipod Hirondellea gigas synthesizes massive quantities of piezolyte proteins. Clearly, Hirondellea gigas is uniquely adapted to survive in the extreme pressure of the Mariana Trench abyss.
The vast majority of cryptographic hash functions utilizing a sponge construction are impervious to length-extension attacks. Furthermore, any cryptographic protocol impervious to length-extension attacks satisfies the strict security mandates of the newly proposed federal standard. It follows inevitably that most cryptographic hash functions utilizing a sponge construction satisfy the newly proposed federal standard's strict security mandates.
Each individual line of code in the autonomous trading algorithm was generated by an open-source routine that lacks any proprietary trade-secret protection. It is therefore evident that the comprehensive autonomous trading algorithm itself cannot qualify for proprietary trade-secret protection.

Matches

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Answer

The medieval codex argument matches the modus tollens deduction; the deep-sea organism argument matches the flawed prerequisite deduction; the cryptography argument matches the restricted generalization deduction; and the trading algorithm argument matches the constituent element fallacy.
Each argument contains a distinct logical skeleton completely independent of its subject matter. The codex argument is a valid contrapositive applying De Morgan's laws. The deep-sea argument is a classic Necessary/Sufficient confusion. The cryptography argument is a valid 'Most-All' quantifier deduction. The algorithm argument is a Fallacy of Composition. The descriptions on the right perfectly articulate these structures using formal logical terminology.

Step-by-Step Solution

1
Deconstruct the logical structure of the medieval codex argument.
Identified as 'If X and Y, then Z. Not Z. Therefore, Not X or Not Y.'
Abstracting the content reveals a valid modus tollens argument acting on an 'and' statement in the sufficient condition.
2
Deconstruct the logical structure of the Mariana Trench organism argument.
Identified as 'X requires Y. Y is present. Therefore, X occurs.'
This reveals a formal logic flaw: mistaking a necessary condition (a prerequisite) for a sufficient one.
3
Deconstruct the logical structure of the cryptographic hash function argument.
Identified as 'Most A are B. All B are C. Therefore, Most A are C.'
This abstraction highlights a valid syllogism combining a majority quantifier ('vast majority'/'most') with a universal affirmative ('any').
4
Deconstruct the logical structure of the autonomous trading algorithm argument.
Identified as 'All parts of X lack property Y. Therefore, the whole of X lacks property Y.'
This is a classic Part-to-Whole flaw, also known as the Fallacy of Composition.
5
Map the abstracted structures to the formal descriptions.
Codex maps to modus tollens; Organism maps to obligatory prerequisite flaw; Cryptography maps to restricted generalization; Algorithm maps to constituent element fallacy.
The formal language in the descriptions perfectly aligns with the abstracted structural skeletons of the stimuli.

Key Concept

Identifying isomorphic formal logic structures and specific logical flaws (Parallel Reasoning and Parallel Flaw)
Question 168Question →

A wildlife conservation team observed that a local population of river otters experienced a substantial increase in breeding success shortly after commercial fisheries in the river basin switched from traditional nylon nets to a newly designed biodegradable netting. The team concluded that the transition to biodegradable netting was directly responsible for the rebound in the otter population.

Which of the following, if true, most strengthens the conservation team's argument?

Show answer & explanation

Answer: Veterinary post-mortem examinations revealed that prior to the switch, entanglement in traditional nylon netting was the leading cause of mortality among breeding-age otters in the river basin.

Answer

The statement showing that entanglement in traditional nylon netting was the leading cause of death among breeding-age otters prior to the switch most strongly strengthens the conclusion.
The conclusion asserts a direct causal relationship between the new netting and the increase in otter breeding success. By establishing that traditional nylon nets were previously the primary cause of death among breeding-age otters, the correct statement provides evidence of the specific mechanism of harm that was eliminated by the switch, thereby strongly reinforcing the causal conclusion.

Step-by-Step Solution

1
Identify the premises and conclusion of the argument.
Premise: Otter breeding success increased after fisheries switched to biodegradable netting. Conclusion: The switch to biodegradable netting directly caused the otter population rebound.
Clarifying the core reasoning helps identify the unstated assumption linking the correlation to direct causation.
2
Identify the reasoning gap in the causal claim.
The author assumes that traditional netting was actively harming breeding otters and that no other concurrent factors caused the recovery.
A strengthener must either demonstrate the causal mechanism or rule out plausible alternative causes.
3
Evaluate the choices to find the statement that best supports the causal link.
Providing physical evidence that traditional nets were directly killing breeding otters establishes the causal mechanism and validates the conclusion.
Showing that the old netting directly impeded breeding-age survival directly connects the policy change to the observed demographic increase.

Key Concept

Strengthening a Causal Argument
Question 169Question →

For each flawed argument presented in the first column, determine the primary reasoning error that it commits. Match each argumentative passage with the abstract description that most accurately identifies its underlying logical vulnerability.

Click a left item, then click its matching right item

Items

Paleoclimatologist: A sudden surge in atmospheric methane concentration is necessary for triggering a rapid transition out of a glacial maximum. Marine sediment cores indicate that atmospheric methane levels spiked drastically at the onset of the Bølling-Allerød interstadial period. Consequently, this dramatic increase in methane was sufficient on its own to precipitate the subsequent global warming.
Aviation Engineer: The composite fuselage designed for our experimental high-altitude glider is constructed entirely from ultra-lightweight carbon-fiber spars and flexible polymer skins. Because every individual spar and skin panel used in the airframe possesses high ductility and flexibility, the completed fuselage as an assembled structure will inherently remain flexible under turbulent aerodynamic stress.
Epidemiologist: Over the past two decades, municipalities that enacted strict water fluoridation standards also documented a 30 percent decline in childhood dental caries. Since the implementation of these municipal standards preceded the recorded improvements in pediatric oral health, the water fluoridation policy was directly responsible for the reduction in caries.
Corporate Litigator: The regulatory commission asserts that our client intentionally manipulated wholesale electricity markets by executing algorithmic cancellations of supply bids. However, the commission's chief investigator has previously published multiple academic treatises expressing hostility toward private utility operators. Thus, the commission's factual finding of intentional manipulation is demonstrably false.

Matches

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Answer

The argument regarding paleoclimatology matches the description of treating a necessary condition as sufficient; the argument regarding the aviation airframe matches the description of illicitly attributing properties of parts to the assembled whole; the argument regarding municipal fluoridation matches the description of inferring causation solely from temporal sequence; and the argument regarding the regulatory commission matches the description of rejecting an allegation based on investigator bias.
Each argument exemplifies a distinct, well-established flaw archetype tested on the LSAT: the paleoclimatologist confuses a necessary condition with a sufficient one; the aviation engineer assumes an aggregate shares all attributes of its parts; the epidemiologist equates temporal sequence with causal agency; and the corporate litigator attacks the author of an allegation rather than addressing the substance of the claim.

Step-by-Step Solution

1
Analyze the formal structure of the first argument (Paleoclimatologist)
The premise states methane is necessary ('necessary for triggering'), while the conclusion claims methane was sufficient ('sufficient on its own').
This isolates the classic necessary versus sufficient condition confusion.
2
Analyze the structural transfer of properties in the second argument (Aviation Engineer)
The premises describe properties of individual parts (spars and panels), while the conclusion asserts the same property holds for the integrated whole (the assembled fuselage).
This identifies the fallacy of composition (part-to-whole inference error).
3
Evaluate the causal reasoning in the third argument (Epidemiologist)
The only evidence offered for a causal link is chronological priority ('preceded the recorded improvements').
This isolates the temporal-causal error (post hoc ergo propter hoc).
4
Examine the evidentiary support in the fourth argument (Corporate Litigator)
The conclusion rejects a claim of fact entirely by pointing to the investigator's personal perspective rather than countering the algorithmic bid data.
This matches the ad hominem / source argument flaw archetype.

Key Concept

Classification of Standard Formal and Informal Reasoning Flaws
Estimated Time:2m 0s
Question 170Question →

Archivists examining medieval mercantile guilds in the Rhine Valley have established the following records:

• Every guild granted an imperial customs exemption operated at least one bonded river quay.
• Some guilds that operated bonded river quays were not permitted to mint local coinage.
• Any guild that maintained a sworn arbitration council was permitted to mint local coinage and held an imperial customs exemption.
• No guild that failed to maintain a sworn arbitration council was authorized to levy warehouse tariffs.

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

Show answer & explanation

Answer: At least some guilds that operated bonded river quays were not authorized to levy warehouse tariffs.

Answer

At least some guilds that operated bonded river quays were not authorized to levy warehouse tariffs.
The correct answer synthesizes the existential premise with two successive contrapositives: the stimulus establishes that some quay-operating guilds lacked permission to mint coinage; lacking minting permission guarantees the absence of an arbitration council; and lacking an arbitration council guarantees that the guild was not authorized to levy warehouse tariffs.

Step-by-Step Solution

1
Formalize the conditional premises and quantifier statement.
Exemption → Quay; Some Quay AND NOT Minting; Council → (Minting AND Exemption); NOT Council → NOT Tariffs (equivalent to: Tariffs → Council).
Translating the stimulus into formal logical relationships clarifies necessary versus sufficient conditions and quantifiers.
2
Take the contrapositive of the council-to-minting relationship.
Since Council → Minting, it follows that NOT Minting → NOT Council.
Failing to satisfy a necessary condition guarantees the absence of the sufficient condition.
3
Chain the derived contrapositive with the tariff restriction premise.
Because NOT Council → NOT Tariffs, combining this yields NOT Minting → NOT Tariffs.
Transitive chaining establishes that any guild unable to mint coinage is strictly barred from levying warehouse tariffs.
4
Apply the existential premise to the derived chain.
There exist guilds operating bonded river quays that cannot mint coinage; therefore, those specific guilds cannot be authorized to levy warehouse tariffs.
Instantiating the existential subset into the valid conditional chain strictly guarantees the conclusion.

Key Concept

Quantifier-conditional synthesis and contrapositive chaining
Estimated Time:1m 50s
Question 171Question →

Nutritionist: Some diet advocates claim that avoiding all dietary fats is necessary for maintaining a healthy cardiovascular system. However, this claim is mistaken. Certain fats, such as omega-3 fatty acids found in flaxseeds and walnuts, actually lower the risk of arterial inflammation and promote heart health.

Which of the following most accurately describes the method of reasoning employed by the nutritionist?

Show answer & explanation

Answer: rejecting a universal claim by providing a specific counterexample that demonstrates its falsity

Answer

Rejecting a universal claim by providing a specific counterexample that demonstrates its falsity
The nutritionist's technique consists of disproving a universal rule ('avoiding all dietary fats is necessary') by presenting a concrete counterexample (omega-3 fatty acids) that contradicts the rule.

Step-by-Step Solution

1
Identify the conclusion of the nutritionist's argument.
The nutritionist concludes that the claim that all dietary fats must be avoided is mistaken.
Finding the conclusion clarifies the main point being defended or refuted.
2
Identify the evidence or premise supporting that conclusion.
Omega-3 fatty acids in flaxseeds and walnuts actually promote heart health and reduce inflammation.
Analyzing the supporting premises reveals how the nutritionist establishes the conclusion.
3
Characterize the logical relationship between the evidence and the claim.
The advocates claimed 'all fats must be avoided' (a universal negative), which the nutritionist refutes by citing a specific instance of a beneficial fat (a counterexample).
Abstracting this interaction matches the standard logical technique of refutation via counterexample.

Key Concept

Refutation of a universal claim using a counterexample
Estimated Time:45s
Question 172Question →

Historians studying a nineteenth-century coastal port observed that merchant shipping logs recorded a sharp decrease in shipwrecks near a treacherous submerged reef following the construction of a lighthouse in 1842. Based on this correlation, the historians concluded that the beam from the new lighthouse was directly responsible for the reduction in wrecks by warning navigators away from the hazard.

Which of the following, if true, most strengthens the historians' argument?

Show answer & explanation

Answer: The total volume of shipping traffic passing near the submerged reef remained constant or slightly increased in the years immediately following 1842.

Answer

The statement showing that shipping traffic near the reef remained steady or increased after 1842 most strengthens the argument.
The argument concludes that the lighthouse beam caused the decrease in shipwrecks. However, a major alternative explanation for fewer shipwrecks is a general decline in the number of ships traveling near the reef. Establishing that shipping traffic stayed constant or increased rules out this rival hypothesis, confirming that the reduction in wrecks was due to improved navigational guidance.

Step-by-Step Solution

1
Identify the conclusion and premises in the stimulus.
Premise: Shipwrecks near a reef declined after a lighthouse was built in 1842. Conclusion: The lighthouse caused the decline by warning navigators away from the reef.
Understanding the core causal claim is essential for determining what logical gap needs reinforcement.
2
Analyze the potential vulnerabilities and unstated assumptions in the causal reasoning.
The author assumes that no other factor, such as a drop in total vessel traffic near the reef, accounted for the decline in recorded shipwrecks.
Strengthening a causal conclusion often involves ruling out plausible alternative causes or confirming that baseline conditions did not change.
3
Evaluate the answer choices to find the statement that best supports the causal link.
Confirming that ship traffic remained steady or increased eliminates the competing hypothesis of reduced traffic, thereby confirming that the rate of wrecks per voyage genuinely declined due to the warning beam.
Ruling out an obvious confounding variable directly substantiates the proposed causal connection.

Key Concept

Strengthening Causal Claims by Ruling Out Alternative Explanations
Question 173Question →

Last year, the city of Riverdale replaced all standard streetlights in its downtown commercial district with much brighter LED lights in an effort to reduce nighttime pedestrian trip-and-fall accidents. However, hospital records indicate that the number of pedestrians treated for injuries resulting from nighttime trip-and-fall accidents in that district increased significantly over the following year.

Which of the following, if true, most helps to resolve the apparent discrepancy described above?

Show answer & explanation

Answer: The improved lighting made the downtown commercial district feel safer at night, leading to a substantial increase in the total number of pedestrians walking there after dark.

Answer

The statement that the improved lighting made the downtown district feel safer at night, leading to a substantial increase in the total number of pedestrians walking there after dark.
The correct response resolves the paradox by demonstrating an increase in the total exposed population. If brighter lights attracted a significantly larger volume of pedestrians downtown after dark, the total number of injuries could rise simply because far more people were walking there, even if the likelihood of any single pedestrian falling was reduced.

Step-by-Step Solution

1
Identify the two conflicting facts presented in the stimulus.
Fact 1: Brighter streetlights were installed specifically to reduce nighttime trip-and-fall accidents. Fact 2: The absolute number of pedestrians treated for nighttime trip-and-fall injuries increased following the installation.
Resolving an apparent paradox requires clearly isolating the two premises that appear contradictory.
2
Determine the underlying causal link needed to reconcile both facts.
A change in the baseline population (total pedestrian foot traffic) can cause the total number of accidents to rise even if the per-person risk of falling decreased.
Total occurrences are the product of the individual probability of an event and the size of the exposed population.
3
Select the choice that provides this reconciling explanation without disputing the stated premises.
The option showing that the brighter lighting brought significantly more people into the district at night successfully bridges both facts.
This allows both the premise regarding improved lighting and the premise regarding higher total hospital visits to be simultaneously true.

Key Concept

Distinguishing between absolute totals and per-capita rates to reconcile unexpected trends
Estimated Time:50s
Question 174Question →

Consider the following flawed arguments and their corresponding reasoning vulnerabilities. Match each argument with the description that most accurately identifies the primary flaw in its reasoning.

Click a left item, then click its matching right item

Items

Conservator: The discoloration observed on the seventeenth-century oil canvas must have been caused by photochemical degradation from ultraviolet light, since extensive chemical testing has conclusively eliminated fungal microbial growth as the source of the damage.
Planetary Geologist: If an exoplanet maintains both a dense nitrogen atmosphere and a robust magnetic field, it is guaranteed to shield surface organic compounds from stellar radiation. Thus, because exoplanet HD 189733b lacks a robust magnetic field, its surface organic compounds cannot be shielded from stellar radiation.
Operations Analyst: Every single machine unit installed in the regional distribution hub operates with zero mechanical downtime during standard processing hours. Consequently, the regional distribution hub as an integrated operational network must operate with zero mechanical downtime.

Matches

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Answer

The conservator's argument matches the description of assuming two explanations are exhaustive; the planetary geologist's argument matches the description of treating a sufficient condition as a necessary condition; and the operations analyst's argument matches the description of inferring a property of an entire system from properties of its constituent parts.
Each argument is paired with its precise structural flaw: the conservator falsely restricts the scope of possible causes to two options; the planetary geologist negates a sufficient condition to conclude the absence of the outcome; and the operations analyst erroneously derives a system-wide property directly from properties of individual machine parts.

Step-by-Step Solution

1
Analyze the first argument (conservator)
The argument rules out one specific cause (fungal growth) and concludes that another specific cause (photochemical degradation) must be the sole explanation without establishing that no other causes could exist.
Identify the structural gap where eliminating one alternative is treated as proof of the only other considered alternative (false dilemma).
2
Analyze the second argument (planetary geologist)
The argument reasons from 'If A and B, then Shielded' to conclude 'If not B, then not Shielded', which is an invalid conditional negation.
Recognize the formal error of confusing a sufficient condition with a necessary condition.
3
Analyze the third argument (operations analyst)
The argument infers that an entire integrated facility has zero downtime because each isolated machine unit has zero downtime.
Identify the composition (part-to-whole) fallacy transferring a component-level attribute to the entire system.

Key Concept

Flaw in the Reasoning: Structural Fallacies (False Dilemma, Conditional Sufficiency vs. Necessity, and Composition)
Estimated Time:1m 30s
Question 175Question →

Soil scientist: Conventional agricultural wisdom holds that planting legume cover crops between growing seasons enriches soil fertility solely by fixing atmospheric nitrogen. However, this view is incomplete. When non-nitrogen-fixing brassica cover crops are planted instead, soil nitrogen retention across subsequent crop rotations matches that achieved with legumes, even though brassicas fix no atmospheric nitrogen at all. Therefore, the primary mechanism by which cover crops preserve soil nitrogen is not biological fixation, but rather the physical prevention of nitrate leaching by dense root networks.

Which one of the following most accurately describes the method of reasoning employed in the soil scientist's argument?

Show answer & explanation

Answer: undermining a proposed explanation of a phenomenon by showing that the phenomenon occurs in the absence of the alleged cause

Answer

The argument proceeds by undermining a proposed explanation of a phenomenon by showing that the phenomenon occurs in the absence of the alleged cause.
The author casts doubt on the claim that atmospheric nitrogen fixation is the sole explanation for nitrogen retention by showing that another plant variety (brassicas) produces the exact same retention effect despite lacking the ability to fix nitrogen. Thus, the argument undermines an explanation by pointing out that the phenomenon occurs in the absence of the supposed cause.

Step-by-Step Solution

1
Identify the target claim and conclusion of the argument
The target claim is the conventional view that legume cover crops enrich soil fertility solely through atmospheric nitrogen fixation. The main conclusion is that the primary mechanism is physical leaching prevention by root networks, not biological fixation.
Accurately identifying the conclusion is essential for mapping the overall argumentative method.
2
Analyze the empirical evidence introduced by the author
The author introduces brassicas—a cover crop that fixes zero atmospheric nitrogen—and shows that soil nitrogen retention is identical to that achieved with legumes.
Understanding the function of the comparative evidence reveals how the author refutes the conventional causal model.
3
Abstract the logical relationship into structural terms
The author demonstrates that effect E (nitrogen retention) persists even when purported cause C (nitrogen fixation) is absent, thereby proving that C is not the sole or primary cause.
Matching this abstract template to the answer choices identifies the correct method of reasoning.

Key Concept

Causal Refutation via Method of Difference / Absent Cause
Estimated Time:1m 15s
Question 176Question →

Editorial: Any municipal infrastructure initiative that receives federal matching funds must undergo an environmental impact assessment. Most municipal initiatives that undergo an environmental impact assessment experience significant construction delays. Therefore, any municipal infrastructure initiative that receives federal matching funds will likely experience significant construction delays.

Which of the following arguments exhibits a flawed pattern of reasoning most similar to that in the editorial's argument?

Show answer & explanation

Answer: Every commercial airliner that operates international routes must maintain satellite communication systems. Most commercial airliners that maintain satellite communication systems undergo quarterly avionics inspections. Therefore, any commercial airliner that operates international routes will likely undergo quarterly avionics inspections.

Answer

The argument concluding that any commercial airliner operating international routes will likely undergo quarterly avionics inspections exhibits the exact same flawed pattern of reasoning.
The correct argument mirrors the exact deductive architecture and quantifier mismatch of the stimulus: it begins with a universal rule placing group A entirely inside group B ('Every commercial airliner on international routes must maintain satellite communication systems'), adds a premise stating that most members of group B possess characteristic C ('Most commercial airliners with satellite communication systems undergo quarterly avionics inspections'), and erroneously concludes that any individual member of group A is likely to have characteristic C ('any commercial airliner on international routes will likely undergo quarterly avionics inspections'). Because group A could reside entirely within the minority of group B that does not possess characteristic C, this inference is logically invalid in the exact same manner as the stimulus.

Step-by-Step Solution

1
Abstract the formal structure and quantifier relationships of the stimulus.
Premise 1: All A (federal-funded projects) are B (undergo environmental assessment). Premise 2: Most B (undergo assessment) are C (experience delays). Conclusion: Therefore, any A will likely be C (each A is likely to experience delays).
Deconstructing the argument into symbolic terms separates logical form from surface content.
2
Identify the underlying logical defect in the stimulus.
The flaw is an illicit quantifier chain / transitivity failure: while A is a subset of B, A could be entirely contained within the minority portion of B that is not C. Hence, one cannot conclude that an individual member of A is likely C.
Parallel flaw questions require matching the precise mechanism of invalidity.
3
Evaluate the answer choices to identify the exact structural match.
The choice concerning commercial airliners states: All A (international airliners) are B (maintain satellite systems). Most B (maintain satellite systems) are C (undergo quarterly inspections). Therefore, any A will likely be C (likely undergo quarterly inspections). This is an exact isomorphic match.
Only an argument matching both the universal-to-majoritarian premises and the individual-probabilistic conclusion replicates the flaw.

Key Concept

Quantifier Transitivity Flaw (All A are B + Most B are C does not entail that A is likely C)
Question 177Question →

Over the past three years, the coastal wildlife preserve of Marelton enforced a strict ban on recreational motorboats in its shallow estuaries to protect endangered eelgrass beds from propeller scarring. However, aerial surveys conducted at the end of the three-year period revealed that the total area of damaged eelgrass beds in these estuaries increased significantly compared to the three years preceding the ban.

Which of the following, if true, most helps to resolve the apparent discrepancy described above?

Show answer & explanation

Answer: A species of invasive herbivorous waterfowl that consumes eelgrass roots, previously kept away from the estuaries by engine noise, colonized the shallows once motorboats were prohibited.

Answer

A species of invasive herbivorous waterfowl that consumes eelgrass roots, previously kept away from the estuaries by engine noise, colonized the shallows once motorboats were prohibited.
The correct answer provides an unconsidered causal consequence of removing the motorboats. If engine noise had been inadvertently keeping away invasive waterfowl that destroy eelgrass roots, banning the boats removed that deterrent, leading to an influx of waterfowl whose feeding damaged more eelgrass than the boat propellers had previously damaged. This allows both facts in the stimulus to be entirely true.

Step-by-Step Solution

1
Identify the two conflicting facts presented in the stimulus.
Fact 1: Motorboats were banned to protect eelgrass from damage. Fact 2: The total damaged area of eelgrass increased significantly after the ban.
Resolving a paradox requires isolating the tension between the intended protective measure and the contrary outcome.
2
Formulate the missing causal link that allows both facts to be true simultaneously.
Need an explanation showing that the motorboat ban inadvertently introduced or facilitated a new source of eelgrass destruction that exceeded the damage formerly caused by boat propellers.
A valid resolution introduces an active mechanism without denying the accuracy of the baseline facts.
3
Evaluate the choices to find the one that bridges the gap through this mechanism.
The statement showing that engine noise previously deterred destructive invasive waterfowl demonstrates that removing the boats allowed the waterfowl to enter and damage the beds.
This bridges the premises by demonstrating an unintended ecological side effect of the ban.

Key Concept

Resolving an apparent paradox by identifying an unconsidered compensatory causal factor
Estimated Time:1m 15s
Question 178Question →

Consider the following argument regarding agricultural soil conservation:

Some agronomists argue that cover cropping is too labor-intensive to justify its adoption on family farms. However, this view fails to account for long-term soil regeneration. Recent agricultural trials demonstrate that cover crops significantly reduce topsoil erosion during winter rains. Reduced erosion preserves vital soil nutrients year after year. Therefore, implementing cover crops ultimately increases long-term farm profitability.

Match each excerpt from the argument to the exact functional role it plays in the reasoning.

Click a left item, then click its matching right item

Items

"Cover cropping is too labor-intensive to justify its adoption on family farms."
"Cover crops significantly reduce topsoil erosion during winter rains."
"Reduced erosion preserves vital soil nutrients year after year."
"Implementing cover crops ultimately increases long-term farm profitability."

Matches

Show answer & explanation

Answer

The statement about cover cropping being labor-intensive matches the counterargument to be undermined; the statement about reducing erosion matches the empirical premise; the statement about preserving vital nutrients matches the intermediate conclusion; and the statement about increasing profitability matches the main conclusion.
Each excerpt fulfills a distinct structural function in the multi-tiered argument: the first is an opposing view introduced to be refuted; the second is trial data acting as a foundational premise; the third is an intermediate conclusion drawn from that data; and the fourth is the overall conclusion supported by the entire chain.

Step-by-Step Solution

1
Identify the author's primary conclusion and opposing viewpoint in the stimulus.
The final sentence asserting that cover crops increase profitability is the primary conclusion, while the initial view of some agronomists serves as the opposing position being challenged.
Establishing the boundary between what the author believes and what opponents believe clarifies the argument's overarching purpose.
2
Trace the structural relationship between intermediate premises and conclusions.
Trial evidence about erosion reduction directly supports the claim that nutrients are preserved, which in turn supports the main conclusion regarding profitability.
Differentiating between basic factual premises and intermediate claims depends on identifying which statements receive and provide support.
3
Align each excerpt with its corresponding argumentative role.
All four statements pair accurately with their distinct roles: counterargument, empirical premise, intermediate conclusion, and main conclusion.
Each structural category has a distinct functional relationship to the overall thesis.

Key Concept

Role in Argument: Identifying Structural Components and Sub-conclusions
Estimated Time:1m 0s
Question 179Question →

Civil Engineer: To ensure that a suspension bridge remains structurally sound under extreme wind conditions, the bridge's main cables must undergo ultrasonic tension testing. The inspection crew completed ultrasonic tension testing on the main cables of the Riverview Bridge last week. Thus, the Riverview Bridge is guaranteed to remain structurally sound during the upcoming severe storm.

Which of the following most accurately describes the flaw in the civil engineer's reasoning?

Show answer & explanation

Answer: treats a requirement that is necessary for structural soundness as though it were sufficient to guarantee that soundness

Answer

The argument treats a condition that is necessary for structural soundness as though it were sufficient to guarantee that soundness.
The argument establishes that ultrasonic testing is required (necessary) for structural soundness under extreme winds. However, completing that test does not rule out other structural vulnerabilities (e.g., foundation failure, deck instability). By concluding that the bridge is guaranteed to remain sound solely because the necessary test was conducted, the author erroneously treats a necessary condition as sufficient.

Step-by-Step Solution

1
Identify the premises and conclusion in the stimulus.
Premise 1: If a suspension bridge remains structurally sound under extreme wind, its main cables must undergo ultrasonic tension testing (Soundness → Ultrasonic Testing). Premise 2: The Riverview Bridge underwent ultrasonic tension testing. Conclusion: The Riverview Bridge is guaranteed to remain structurally sound.
Deconstructing the argument into formal components isolates the structural relationship between conditions.
2
Analyze the logical validity of the inference.
The premises state that ultrasonic testing is a required (necessary) condition for soundness. The conclusion infers that because this requirement is met, soundness is guaranteed (sufficient).
This is a classic conditional logic error: affirming the consequent / confusing necessary and sufficient conditions.
3
Match the identified reasoning vulnerability to the option choices.
The statement describing the confusion of a necessary condition with a sufficient condition accurately captures this exact reasoning error.
The correct answer in an LSAT Flaw question must describe precisely what the argument did wrong.

Key Concept

Necessary versus Sufficient Conditions (Conditional Reversal)
Estimated Time:1m 15s
Question 180Question →

Every industrial facility that implements closed-loop solvent recycling reduces its hazardous wastewater discharge by more than 80 percent. No industrial facility operating in the river basin reduced its hazardous wastewater discharge by more than 80 percent last year unless it received a green modernization subsidy from the municipal environmental authority. Furthermore, any facility that received a green modernization subsidy was subject to unannounced quarterly compliance audits. Apex Chemical, an industrial facility operating in the river basin, was not subject to unannounced quarterly compliance audits last year.

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

Show answer & explanation

Answer: Apex Chemical did not implement closed-loop solvent recycling last year.

Answer

Apex Chemical did not implement closed-loop solvent recycling last year.
The correct inference strictly follows from contrapositive deduction along the conditional chain. The stimulus establishes that for any facility operating in the river basin, implementing closed-loop solvent recycling guarantees a wastewater discharge reduction of over 80 percent, which in turn requires receiving a green modernization subsidy, which in turn requires being subject to unannounced quarterly compliance audits. Because Apex Chemical operates in the basin and was not subject to quarterly audits, it could not have received the subsidy, could not have achieved the discharge reduction, and therefore could not have implemented closed-loop solvent recycling.

Step-by-Step Solution

1
Map the conditional statements in the stimulus into formal logical relationships.
Statement 1: Closed-Loop Recycling →\rightarrow Discharge Reduction >80%>80\%. Statement 2 (for basin facilities): Discharge Reduction >80%→>80\% \rightarrow Modernization Subsidy. Statement 3: Modernization Subsidy →\rightarrow Quarterly Audits.
Establishing the precise direction of conditional requirements allows for valid contrapositive chaining.
2
Chain the conditional statements for an industrial facility operating in the river basin.
For any basin facility: Closed-Loop Recycling →\rightarrow Discharge Reduction >80%→>80\% \rightarrow Modernization Subsidy →\rightarrow Quarterly Audits.
Combining the premises establishes that undergoing quarterly audits is a necessary condition for any basin facility that implemented closed-loop recycling.
3
Apply the contrapositive to the factual information provided about Apex Chemical.
Apex Chemical is in the river basin and was NOT subject to quarterly audits. By contrapositive: Not Audited →\rightarrow No Subsidy →\rightarrow No Discharge Reduction >80%→>80\% \rightarrow No Closed-Loop Recycling.
Denying the necessary end condition guarantees the denial of all preceding sufficient conditions in the chain.

Key Concept

Multi-premise conditional deduction via contrapositive chaining
Estimated Time:1m 45s
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