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Help#Questions about match the flaw questions

cklomoooooo-1cklomoooooo-1 Alum Member
edited October 2021 in Logical Reasoning 128 karma

I saw this on some LSAT prep book:
Question: for example in a mistake necessary as sufficient question,
Premise: If A then B.
Conclusion: B therefore A.

Given two answer choices
1) If A then B, and if B then C.
C, therefore A.
2) if A then B, not A, therefore not B.

Should we choose the one with additional premise or the one with contrapositive conclusion?

Comments

  • Habeas PorpoiseHabeas Porpoise Alum Member Sage
    edited October 2021 1861 karma

    I feel like this is risky enough (with students complaining that both answers are right) that LSAC wouldn't give both in the same question unless the stimulus matched one exactly. But if I had to pick I'd lean towards (1). In the end A --> B, B--> C is just A --> C. If we then erroneously say C, therefore A, it's generally the same as the stimulus since we're affirming the necessary condition in both cases.

  • cklomoooooo-1cklomoooooo-1 Alum Member
    128 karma

    Thank you!! Yes, I've seem both happened to be correct in the past. This is actually from The LSAT Trainer, and Mike Kim chose 1) as well. > @"Habeas Porpoise" said:

    I feel like this is risky enough (with students complaining that both answers are right) that LSAC wouldn't give both in the same question unless the stimulus matched one exactly. But if I had to pick I'd lean towards (1). In the end A --> B, B--> C is just A --> C. If we then erroneously say C, therefore A, it's generally the same as the stimulus since we're affirming the necessary condition in both cases.

  • Habeas PorpoiseHabeas Porpoise Alum Member Sage
    1861 karma

    No problem! :)

  • WinningHereWinningHere Monthly Member
    397 karma

    Yeah whatever is the match!

  • kerenaaakerenaaa Alum Member
    49 karma

    def the match. additionally, answer choice 2 would actually be a mistaken negation- confusing the sufficient for necessary

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