Question about Parallel Reasoning Structures Forum

[echoplasm]

This is a dumb question, but I've searched the answer to no avail.

I'm trying to garner the most tips and tricks I can for the LSAT. In parallel reasoning questions, does the structure in the correct answer have to match what is in the stimulus, thus contrapositives would NOT be correct ever? By this I mean, say the question goes like this:

1. A --> B

This means we have to find the same structure in the answers, i.e. X --> Y. However, what if one of the answer choices is the contrapositive of the stimulus, i.e. ~B-->~A? Would that ever happen on a parallel reasoning question? I have yet to come across one (but then again, I've only done a few preptests.)

[Dave Hall]

This is a dumb question, but I've searched the answer to no avail.

I'm trying to garner the most tips and tricks I can for the LSAT. In parallel reasoning questions, does the structure in the correct answer have to match what is in the stimulus, thus contrapositives would NOT be correct ever? By this I mean, say the question goes like this:

1. A --> B

This means we have to find the same structure in the answers, i.e. X --> Y. However, what if one of the answer choices is the contrapositive of the stimulus, i.e. ~B-->~A? Would that ever happen on a parallel reasoning question? I have yet to come across one (but then again, I've only done a few preptests.)

Not a dumb question!

Yes, the contrapositive can be (and has been, rarely) the correct answer in just the manner you've described.

This makes some sense: after all, the contrapositive has precisely the same meaning as the original condition. Both are saying that B is necessary for A. So if you don't have B, you can't have A.

Hope that helps,

d