Help#Questions about match the flaw questions

cklomoooooo-1

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?

Habeas Porpoise

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-1

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 Porpoise

No problem!

WinningHere

Yeah whatever is the match!

kerenaaa

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