#7 - Failure to rotate crops depletes the soil's nutrients

[eober]

Hi,

Thank you so much for clarifying! Is it better to think about this stimulus without drawing the conditional reasoning? I got confused with that.

Thanks!

[MIA179]

I have read an earlier post, reread the stimulus on multiple counts, used LR Bibles techniques and still having trouble understanding how the formal logic behind this question works. In addition, I can't seem to grasp the stimulus itself. I have done well in other MBTs however, this one really has given me a headache. Any tips on how to tackle this question? Also why is "Failure to rotate crops depletes the soil's nutrients gradually unless other preventative measures are taken."
~RC + ~PM -> SD
How is the "and" inferred?
Also, would this be considered an easy question, should I worry?
Any help would be greatly appreciated.

[Nikki Siclunov]

Hi MIA179,

Thanks for your question! Here's how I would diagram the conditional language here:

First sentence:

NOT rotate crops and NO other measures Deplete nutrients

Second sentence:

Deplete nutrients and NO fertilizer Crops cannot be grown

The stem proposes that crops were grown, but fertilizer wasn't applied, and then asks us what must be true. If the crops are grown, by the contrapositive of the second sentence we know that either fertilizer was applied, or else the soil's nutrients were not depleted. But, since fertilizer apparently wasn't applied, we can automatically conclude that the soil's nutrients weren't depleted. This conclusion triggers the contrapositive of the first chain: if nutrients weren't depleted, then either the crops were rotated, or else some other measures were taken. These deductions are consistent with answer choice (C).

Does that make sense? Let me know.

Thanks!

[MIA179]

Nikki,

I want to begin by thanking you for taking your time in helping me.

This definitely helped understanding the formal logic aspect. And although I see how understanding the first and second set conditionals can help to prephase the answer choices, I believe in this particular example the ending of the stimulus makes (C) clear as the correct answer choice (Please correct me if I am wrong). With that said, for questions of similar character would you suggest writing out the logic behind the argument? Or are these types of questions also excluded from writing out if one hopes to reach 160+? I am worried that because I was not able to do so I could get stuck on these types on test day. In addition, would you consider this type of question (by type I mean the amount of conditional logic behind the argument) a common type of MBT question? Sorry for the compact questions.

Hope to hear from you soon,

MIA179

[Nikki Siclunov]

Hi MIA179,

LR questions with stimuli containing conditional reasoning are quite common on the test, accounting for 10-15% of all questions. Usually, conditionality is tested in the context of Must Be True, Justify, Parallel/Flaw, and Cannot Be True questions, though it can appear in any question type.

To answer your question about whether you should diagram every stimulus containing conditional reasoning, the answer is - it depends If a diagram helps - and it does, in most cases - then yes, you should. Creating a diagram certainly carries a cost (time), but - assuming that it is correct - makes it virtually impossible to miss the question. Conditional diagraming is especially helpful whenever the stimulus contains multiple conditional statements, and also when it uses complex language ("unless," "without," "only if," etc.) to convey the conditional relationship.

Hope this helps a bit!

[Dave Killoran]

Hi MIA179,

I actually wrote a blog about diagramming conditionality in LR that might help a bit here: http://blog.powerscore.com/lsat/bid/333 ... To-Diagram

Please check that out and let me know what you think. Thanks!

[lbevins]

I see two different forms of diagramming posted. Can someone confirm the entire diagram for this question .

[Dave Killoran]

I see two different forms of diagramming posted. Can someone confirm the entire diagram for this question .

Hi L,

In order to help us answer your exact question, can you point us to precisely what you are referring to? Is it the different sentences being discussed, or a representation issue?

Thanks!

[na02]

Hi,

I've read through the previous posts and am having trouble seeing the proper way of diagramming..
I think it's because I'm reading through the LRB and there's an example with tables & waiting & reservations.

There, it says:
"Table wait"

If unless comes in:

"~(Table wait) reservation"

This then means:

Table wait OR reservation

in other words,

~wait AND ~reservation table



How is this similar to the question?

~Rotate depletes nutrients

Putting in the unless:

~(~Rotate depletes nutrients) preventive measures

So according to the LRB, it would become:

~Rotate depletes nutrients OR preventive measures

I don't see how this turns into the previous post:

~Rotate AND ~preventive measures depletes nutrients

Because in the former case, wouldn't the contrapositive be:

~depletes nutrients AND ~preventive measures Rotate



If anyone could clear up my confusion.. Thank you!

[Jeremy Press]

Hi na02,

The reason the LRB example doesn't directly translate diagrammatically to the first sentence of question #7 is that the LRB has as its sufficient condition something that's stated in positive terms (If you're going to get a table, then you have to wait), whereas the first sentence of question #7 has as its sufficient condition something that is stated in contrapositive terms, i.e. negatively (if you don't rotate crops, then you'll lack nutrients). In order to see the correspondence between the LRB and the diagramming Nikki and Steve helpfully recommended, turn that sufficient condition portion of the first sentence of question #7 into its positively-framed contrapositive: "If you're going to maintain soil nutrients, then you must rotate crops." Doing that, we can apply the steps of the diagrammatic construct from the "Table/Wait/Reservation" LRB example and get where Nikki and Steve are correctly taking us:

1. ~(Maintain nutrients Rotate) Preventative Measures

2. Maintain nutrients Rotate OR Preventative Measures

3. ~Rotate and ~Preventative Measures Deplete nutrients

I hope this helps!

Jeremy