Logical Reasoning Problem Set #1, Question #49

[ronnieronnie]

Hi Guys,

Could you explain for me why E is the correct answer here? I selected B, but realize that language may be too strong, and I ruled out E because the stimulus says a 10% production increase is necessary, they may be unable to increase productivity by 20% but I thought 10% could still save them from bankruptcy. Why is this not so?

Thanks,
Ronnie

[Dave Killoran]

Hey Ronnie,

You've run into one of the classic LSAT questions of all time, from the June 1992 LSAT (LR 1, #25), and this is an excellent question to test your understanding of conditional reasoning. Let's look at the stimulus first.

The second part of the first sentence often confuses students, and understanding the relationship here makes or breaks you on this question (but it looks like you understood the necessity of the 10 percent, which is good). Essentially, if they don't go bankrupt, what must have happened? They increased productivity 10 percent. That would be diagrammed as:

B 10

The second sentence is a bit of a strange one, and establishes that if they can get 10 percent, then 20 percent is attainable. That diagrams as:

10 attain 20

That's an odd concept (if you can get 10, then it's necessary that you can attain 20), but that's what the author says, so we'll work with it.

Combined, of course, the two diagrams create the following chain:

B 10 attain 20


So, looking at answer choice (B), you can see that it is actually a Mistaken Reversal, a classic wrong answer in a Must Be True question that features conditional reasoning.

Answer choice (E) is a contrapositive, and thus correct in a Must Be True question.

Please let me know if that helps. Thanks!

[ronnieronnie]

Hi Dave,

I did not diagram the question! So I didn't even realize it made use of conditional reasoning until you pointed it out. I have to go back and practice identifying question stems because that's gotten me in trouble in the past and that's part of the trouble I had in this question. I also need to review conditional reasoning because that is also one of my problem areas and I did not pick up on the conditional language.

Thanks for explaining,
Ronnie

[Dave Killoran]

No problem--glad to help. You don't always have to physically diagram conditional statements, but in this case you can see how important it is to at least recognize that it is here. Keep working at it and you'll get better!

Good luck!