Q3 - Whenever Joe's car is vacuumed

[ohthatpatrick]

What does the Question Stem tell us?
Match the Reasoning

Break down the Stimulus:
Conclusion:
K&L Fixed car.

Evidence:
Car got vacuumed --> K&L Vacuumed it.
K&L Vacuumed it --> K&L Fixed car.
Car got vacuumed.

Any prephrase?
We're looking for three premises: two conditionals that chain together to give us an A -> B -> C chain, and a statement of fact that gives us A. The conclusion is a statement of fact that gives us C.

Correct answer:
A

Answer choice analysis:
A) Wet -> DW Morn. DW Morn --> Meds. Wet. Therefore, Meds.

B) clear mismatch because of the either/or

C) Missing the two conditional statements

D) The conclusion itself is a conditional statement. Also, there are only two premises. So we have the A - > B -> C chain, but not the statement of fact that triggers the chain. Finally, the conclusion is an illegal reversal.

E) clear mismatch because of the either/or

Takeaway/Pattern: Counting the number of premises in your recipe can be a nice shortcut (although there are times when the answer is the "best" match, not a perfect match). Also, focusing on types of claims in the premise and conditional (2 conditional premises, 1 factual premise, 1 factual conclusion) helps get rid of answer choices that have either / ors, lack conditionals, or have conditional conclusions.

#officialexplanation

[cdc3d]

I know I'm missing something here. I diagrammed the argument in the stimulus as:
V → E; E → F; V → F
The only option that came close to modeling this form was answer (A): W; D → W; M → D; M

The correct answer is (B), but that answer presents a choice between two alternatives. Because the one alternative did not occur, the other must have occurred: H; H or B; ~B. How is this the same form of reasoning as presented in the stimulus? Am I over analyzing this?

Thanks for your help.
-Chelsea

[noah]

Chelsea, you rock. The answer is (A). Answer key matrix glitch?

If anyone else needs this question explained:

The stimulus provides us the following:

V --> KL V
KL V --> KL F
V
Therefore, KL F

And, the argument works since if you know V, you can go down the chain: V --> KL V --> KL F

(A) has the same structure, albeit in a different order:

W
W --> DW Morn
DW Morn --> Med
Therefore, Med

(B) is a clear mismatch because of the either/or

(C) has a different structure; it's missing the two conditional statements.

(D) is tempting, however it ends up providing this:

L Grump --> ~ C Morn
~ C Morn --> Runs out coff.
Therefore, Runs out coff --> L Grump.

It starts out promising, but it should have ended with L Grump, therefore Runs out coff.

Instead it ends with a reversal of logic, and it ends with a relationship, whereas the stimulus ends with simply stating one phenomenon.

(E) is a clear mismatch because of the either/or

[cdc3d]

Thanks, Noah! I feel infinitely more confident now! I must have looked at that darn question for thirty minutes trying to figure out what I was missing...

[jhouseut]

Chelsea, I believe you have the chain backwards for choice (A)

wet only if drank morning

w--> dm

only time drinks is when taking meds ("aka" drinking requires meds) - I was momentarily set off track because i usually look for only as the neccessary condition indicator, however the meaning here is slightly different. Paraphrasing the statement made it easy to come up with the SN conditional

dm --> meds

premise chain
w: w-->dm--->meds

conclusion: meds

[noah]

You're 100% correct. Please ask jhouseut about this question for now on

[aust1n_chen]

jhouseut's logic seems correct but I am having a hard time understanding why it is:
DWM --> MED ...
when "MED" is introduced with a suff indicator 'when' and "DWM" is introduced with nec indicator 'only'

I first wrote MED --> DWM which of course doesn't work, any explanation would be appreciated!

[noah]

DWM --> MED ...
when "MED" is introduced with a suff indicator 'when' and "DWM" is introduced with nec indicator 'only'
!

Good question. Interestingly, this question comes up a lot when I work with people who have studied the LSAT already with some well-known books. I think what happens is that people get into a mind frame of simply looking for trigger words to indicate the logic. Instead, grasp the meaning.

To get into the word play, the "only" in this sentence is actually applying to taking the medication. Think about these two sentences:

I'm happy only when I'm in the mountains.

The only time I'm happy is when I'm in the mountains.

They mean the same thing!

I suggest you use the "only" to tell you that there is a necessary condition and then go find it, but use a more intuitive approach at that point. Frankly, this sort of switch rarely comes up, but struggling with it reveals a rigidity that could be slowing you down.

Let me challenge you a bit: Why is (D) wrong? And what should it say in order to be correct?

[jamiejames]

If the stim introduces "only" in the form of "the only," then whatever "the only" is mofidyfing is sufficient. If it is "only" by itself, then the next thing is neccessary, same with "only if"

Can someone tell me im wrong on that?

[timmydoeslsat]

You are correct in your thinking. I just want you to not be so formulaic when you read a statement. For example:

I only clean my jeep when it is sunny outside.

This is really an "only when" situation even though the word only appears to be by itself.

I like what Mike.Kim advises on formulating conditionals, think about what you know for sure.

If I clean my jeep....it is sunny outside.

That is what this statement is telling me.

[noah]

If the stim introduces "only" in the form of "the only," then whatever "the only" is mofidyfing is sufficient. If it is "only" by itself, then the next thing is neccessary, same with "only if"

Can someone tell me im wrong on that?

As Timmy above says, that seems to hold water. But, why not understand the statements instead of trying to memorize all the possible terms? There's a limit to what you can achieve memorizing the LSAT...

[jamiejames]

If the stim introduces "only" in the form of "the only," then whatever "the only" is mofidyfing is sufficient. If it is "only" by itself, then the next thing is neccessary, same with "only if"

Can someone tell me im wrong on that?

As Timmy above says, that seems to hold water. But, why not understand the statements instead of trying to memorize all the possible terms? There's a limit to what you can achieve memorizing the LSAT...

Oh for sure, I agree. I've done so many of these questions that I now understand outside the realms it memorizing which way round to place it. Like if I said "the only tree in the world is on fire" that means that this is the last tree left, therefore every single one is on fire, so it goes in the "sufficient" spot (before the arrow" then fire goes in the necessary spot (after the arrow). Thanks guys