Logical ReasoningDifficulty: Hard

PT106 S2 Q20 Explanation

The report released by the interior

A free, expert breakdown of this official LSAT Logical Reasoning question.

TopicsParallel Flaw

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Stimulus

The report released by the interior ministry states that within the past 5 years the national land-reclamation program has resulted in a 19 percent increase in the amount of arable land within the country. If these figures are accurate, the program has been a resounding success. Senator Armand, a distinguished mathematician and successful. Clearly, therefore, the figures cited in the report cannot be accurate.

What this question is testing

Parallel Flaw

Your task

Break the argument into its conclusion and evidence, then do exactly what the question stem asks with that structure.

Common trap

Answers that sound relevant to the topic but don't connect to the argument's actual reasoning.

Winning move

Predict what a right answer must do, then test each choice against the conclusion-evidence gap.

Reading along? Open the full official question in LawHub — we show a fragment here and keep the reasoning in our own words.

The question
20.

The argument above exhibits an erroneous pattern of reasoning most similar to that exhibited by which one

Answer choices

  1. Weak Premise Match1% picked this

    Albert’s father claims that Albert does not know where the spare car keys are hidden. Yesterday, however, Albert reported that he had discovered the

    This argument doesn't have the implication of the original claim. It also doesn't have an "expert" source debunking an implication of the original claim. The original argument was like Premise 1: Source 1 claims Y is true. Premise 2: If Y is true, Z is true. Premise 3: But this trusted source says Z can't be true. Conclusion: Thus Y can't be true. This argument doesn't have any conditional like P2. And source 2 is not being identified as a very credible source. This answer is more like this: Premise 1: Source 1 claims Y is true. Premise 2: But source 2 contradicted claim Y. Conclusion: Thus claim Y isn't true. Our only objection to this argument would be "what if Albert was wrong or lying in terms of what he claimed?" That's fairly close to the original, but it seems way more fair to trust Albert when it comes to whether or not he knows where the spare keys are than it did to trust some random Senator who's good at math about whether arable land has increased.

  2. Weak Premise Match3% picked this

    Gloria’s drama teacher claims that her policy is to give each student the opportunity to act in at least one play during the year

    This one is just like (A). We have a source 2 contradicting something source 1 said or implied, and the conclusion is still flawed because it's overconfidently certain that source 2 is providing good info. But, again, it lacks the Inappropriate Authority aspect of the original. It's reasonable to trust Gloria, who attended every class, when it comes to whether she was given an opportunity to act in at least one play. We shouldn't be 100% sure, but trusting Gloria is way safer than trusting the Senator, who was more external to the thing being discussed (unless the Senator is somehow part of the land-reclamation project, but we weren't told that).

  3. Weak Premise Match22% picked this

    Amos claims that he can hold his breath under water for a full hour. Dr. Treviso, a cardiopulmonary specialist, has stated that humans are

    This one is just like (A) and (B). It does have Source 2 contradicting something that Source 1 said or implied, and it unconditionally sides with Source 2. But again it lacks the Inappropriate Expert part of the original argument. It sounds like Dr. Treviso is just the right kind of expert you'd trust to judge whether someone is physiologically capable of holding their breath for 30 mins.

  4. Wrong Flaw5% picked this

    Evelyn reports that she got home before midnight. Robert, who always knows the time, insists that she did not. If Robert is right, Evelyn

    This has Source 2 contradicting Source 1, but Source 2 is always right about the thing he's talking about (time). Furthermore, the last couple ideas here get into a different flaw: Necessary vs. Sufficient confusion. If Robert is right, Evelyn couldn't hear late news. According to Evelyn, she didn't hear the late news. (that establishes the outcome, but we're not allowed to derive the trigger from that). Yet, the author does go and conclude that since the outcome was true, the trigger must be true; Robert must be right, which means Evelyn was wrong.

  5. Correct69% picked this

    Moira, after observing the finish of the 60-kilometer bicycle race, reports that Lee won with Adams a distant third. Lomas, a bicycle engineering expert,

    Why this is right

    Again we have Source 2 contradicting Source 1, but this time Source 2 is an Inappropriate Expert (just like in the original), whereas source 1 actually seems like a more knowledgeable party. Moira actually observed the end of the race, whereas Lomas is just an expert on how bikes get made. If the issue at hand is "did Lee finish ahead of Adams?", it seems like Source 1 is the more trustworthy source.

    Skill tested: Parallel Flaw · how this choice captures the argument's function is the move to repeat next time.

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