LSAT Logical Reasoning Practice Set 4 Practice Questions with Answers

7,500 students take the LSAT during a typical testing window, and many find the Logical Reasoning section to be the most demanding part of the exam. This specific section requires a high degree of precision in identifying premises, conclusions, and the underlying assumptions that bridge them. By working through this LSAT Logical Reasoning Practice Set 4, you can refine your ability to spot logical fallacies and strengthen your analytical skills. Success on this portion of the exam is not just about reading quickly; it is about deconstructing arguments to see how they function or fail. For those looking for a structured approach to the entire exam, our LSAT Prep hub offers a centralized location for all your study needs.

Concept Explanation

Logical Reasoning on the LSAT consists of short arguments or sets of facts followed by a question that asks you to analyze the relationship between the evidence and the conclusion. Each stimulus is designed to test your ability to identify the main point, find hidden assumptions, strengthen or weaken an argument, or identify a flaw in the reasoning process. The Law School Admission Council (LSAC) structures these questions to mirror the analytical tasks required in law school and legal practice. Understanding the "core" of an argument—the transition from premise to conclusion—is the most critical skill for this section. You should also be familiar with critical reasoning principles which overlap with many LSAT concepts. A systematic approach involves reading the question stem first, identifying the argument's components, and then predicting the answer before looking at the choices.

Solved Examples

1. Example: Identifying the Conclusion
   Stimulus: Many people believe that eating carrots improves night vision. However, while carrots contain Vitamin A which is essential for eye health, there is no evidence that consuming them in excess provides any benefit beyond normal vision. Therefore, the claim that carrots give you "super" night vision is a myth.
   Step 1: Locate the conclusion marker. The word "Therefore" signals the final claim.
   Step 2: Identify the premises. The premises are that Vitamin A is essential but excess does not add extra benefit.
   Step 3: State the conclusion. The conclusion is that the idea of carrots providing super night vision is a myth.
2. Example: Flaw in Reasoning
   Stimulus: Every time the local football team wears their red jerseys, they win. They are wearing their red jerseys today, so they will definitely win.
   Step 1: Analyze the logic. The argument assumes that a past correlation guarantees a future result.
   Step 2: Identify the flaw. This is a "correlation vs. causation" or "false prediction" flaw. Just because it happened before doesn't mean it must happen again.
   Step 3: Formulate the flaw description. The argument treats a historical coincidence as a sufficient condition for a future victory.
3. Example: Necessary Assumption
   Stimulus: To reduce traffic congestion, the city must build a new subway line. Building the subway line will cost $500 million.
   Step 1: Find the gap. The argument concludes a subway is necessary but mentions a specific cost.
   Step 2: Identify the assumption. The argument assumes the city can actually afford or obtain the $500 million needed.
   Step 3: Apply the Negation Test. If the city cannot obtain the money, the plan to build the subway is impossible, thus the argument fails.

Practice Questions

1. The mayor claims that the new park will increase property values in the neighborhood. However, property values in the neighboring town decreased after a similar park was built. Thus, the mayor's claim is likely false.

2. No one who is a member of the chess club is also a member of the wrestling team. Sarah is a member of the chess club. It follows that Sarah is not on the wrestling team.

3. If a plant is a cactus, it requires very little water. This plant is not a cactus. Therefore, this plant requires a lot of water.

4. All successful entrepreneurs are risk-takers. Some risk-takers are not successful entrepreneurs. Therefore, being a risk-taker is a necessary but not a sufficient condition for being a successful entrepreneur.

5. Recent studies show that people who drink green tea daily have lower rates of heart disease. Therefore, drinking green tea causes a reduction in heart disease risk.

6. Scientists have discovered a new species of bacteria that thrives in extreme heat. Because this bacteria was found near a volcanic vent, it must be able to survive temperatures exceeding $100^\circ \text{C}$.

7. The company's profits rose by 20% this year. The CEO argued that this increase was due entirely to the new marketing campaign. However, the overall industry saw a 25% growth during the same period.

8. If the library is open, then the students are studying. The students are not studying. Therefore, the library is not open.

9. A study found that children who play musical instruments perform better on math tests. The researchers concluded that music lessons improve mathematical ability.

10. Most voters in the district support the incumbent. Jane is a voter in the district. Therefore, Jane likely supports the incumbent.

Answers & Explanations

1. Answer: The argument uses a faulty analogy. The author assumes that because a park failed to raise values in a different town, it will also fail here. This ignores potential differences between the two locations or the types of parks built.
2. Answer: Valid Deductive Reasoning. This follows the structure: If $A \rightarrow \text{not } B$. $A$ is true. Therefore, $\text{not } B$. It is a logically sound application of a negative relationship.
3. Answer: Mistaken Negation. The premise states $\text{Cactus} \rightarrow \text{Little Water}$. The author incorrectly concludes $\text{not Cactus} \rightarrow \text{not Little Water}$. A non-cactus might also require little water (e.g., a succulent).
4. Answer: Valid Reasoning. If all entrepreneurs are risk-takers, you must be a risk-taker to be an entrepreneur (necessary). If some risk-takers are not entrepreneurs, then risk-taking alone doesn't guarantee success (not sufficient).
5. Answer: Correlation vs. Causation. The argument assumes that because two things happen together, one causes the other. It ignores potential "third factors," such as green tea drinkers having generally healthier diets.
6. Answer: Strengthened by an Assumption. The argument assumes the volcanic vent area actually reaches those temperatures. If the vent water is $80^\circ \text{C}$, the conclusion doesn't necessarily follow.
7. Answer: Weaken the CEO's claim. By showing the industry grew more than the company (25% vs 20%), the argument suggests the marketing campaign might actually have been ineffective, and the company just rode a general market wave.
8. Answer: Valid Contrapositive. The logic follows: $L \rightarrow S$. $\text{not } S$. Therefore, $\text{not } L$. This is a standard valid inference in formal logic.
9. Answer: Causal Flaw. Similar to question 5, this assumes music causes math skill. It could be that naturally analytical children are drawn to both music and math.
10. Answer: Probabilistic Reasoning. This is a strong inductive argument. If "most" (more than 50%) do something, it is "likely" that a random member of that group does it too.

Frequently Asked Questions

How is Logical Reasoning different from Reading Comprehension?

Logical Reasoning focuses on the structural integrity and validity of short arguments, whereas Reading Comprehension tests your ability to synthesize information and identify themes across long passages. While both require close reading, Logical Reasoning is much more focused on formal logic and identifying specific fallacies.

What is the "Negation Test" in LSAT prep?

The Negation Test is a technique used for Necessary Assumption questions where you logically negate an answer choice to see if it destroys the argument. If the argument falls apart when the choice is made false, then that choice is a necessary assumption.

How many Logical Reasoning sections are on the LSAT?

Currently, the LSAT includes two scored Logical Reasoning sections, making it the most significant portion of your total score. This emphasizes the importance of mastering these question types through sets like textual analysis sets and logic drills.

Can I use outside knowledge to answer these questions?

No, you should only use the information provided in the stimulus and common-sense definitions of words. Bringing in outside scientific or historical facts can often lead you to choose "distractor" answers that are factually true but logically irrelevant to the specific argument provided.

What is a "Sufficient Assumption"?

A sufficient assumption is a statement that, if added to the premises, would make the conclusion 100% logically certain. Unlike a necessary assumption, it doesn't have to be true for the argument to work, but if it is true, it "plugs the gap" perfectly. You can practice similar logic gaps using the AI Question Generator for customized drills.

Why are "Flaw" questions so common?

Flaw questions are frequent because they test your ability to see the difference between what was said and what was actually proven. Identifying common errors like ad hominem attacks, circular reasoning, and straw man arguments is essential for legal reasoning and high LSAT scores.