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#23- At Southgate Mall, mattresses are sold only at Mattress

SLF
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With regard to LSAT #54, Section #2, Question #23, how do I "process" the stimulus and each of the answer choices in such a way that I can identify the correct answer in a timely fashion?

Feel free to ignore what follows and just answer with your strategy/approach. Or, if you wish to know what I did, my approach was to label the components as follows:

Southgate Mall = Diane's Apartment = A
Mattresses = Food = X
Mattress Madness = Refrigerator = Y
20% Discount = Purchased Within Last Week = C

With these labels, I then patterned the stimulus as:

At A, X only at Y ... every X at Y is C ... so every X at A is C

From there, I patterned the answer choices as:

A) At A, only X is in Y ... all X is C ... so, all X in A is C
B) At A, all X is in Y ... all X in Y within C
C) At A, all X is in Y ... all X in Y was C ... so all X in A is C
D) At A, only X is in Y ... all X in Y was C ... so all X was C and is in A
E) Only X in C is in Y ... All X that was C is in A ... so all X in A is in Y

This gets the job done...and it points out that 'C' is the correct answer but it was quite time-consuming...not to mention that all the markings make it easy to get things confused and mixed up.
Lucas Moreau
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Hello, SLF,

I have good news and bad news. The bad news is that there really isn't a less time-consuming way of milling through a problem like this than the one you used, since there are so many moving pieces in the stimulus. The good news is actually the same news, though: you've found the very best approach already. ;) That diagram is more or less exactly what I would have told you to do.

Parallel Reasoning questions are some of the toughest not because of their native difficulty (well, not mainly...), but because they're just so darned time-consuming. If you're going to skip any questions, these are good candidates. Remember that every question is worth exactly as much as every other - it's never a good idea to spend 2, 3, 4 minutes or more on a single question!

Hope that helps,
Lucas Moreau
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SLF
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Thanks so much!
avengingangel
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To confirm, this is valid reasoning, yes?
Emily Haney-Caron
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Hi avengingangel,

Yep, it is. If you diagram it out, you should be able to eyeball it and see that, since the reasoning here is pretty simple. Good work identifying that!
hassan66
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I am having trouble with B and C. The only difference between answer choice B and C is their first sentence which was diagrammed the exact same in the above diagrams. Otherwise, the second and third sentences in both say "Diane purchased all the food in her refrigerator within the past week. Therefore, she purchased all the food in her apartment within the past week."
Adam Tyson
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I do think there is an error in the diagrams done by the student earlier in this thread, and you should not rely on those diagrams but should instead do your own. Did you approach this with diagrams? I would recommend it!

My quibble with the earlier provided diagrams is with answer the first part of B, which should actually be:

Y and all the X that is in Y are all within A

That's not a match to the stimulus, so it is out right away!

Try doing your own diagram, maybe one that is less abstract, and you'll see the key difference for yourself.
Adam M. Tyson
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ataraxia10
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Hello, I used a diagram that was simpler but not very precise. I narrowed down the choices to A & C from just reading the choices and applied the diagram to decide between the two contenders.

Premise:
At Southgate Mall, mattresses are only sold ---> at Mattress Madness
A ---> B
Every mattress at Mattress Madness ----> is on sale at a 20 percent discount
B ----> C
Every mattress for sale at Southgate Mall ----> is on sale at a 20 percent discount
A ----> C

Choice A:
The only food in Diane's apartment ----> In her refrigerator
A ------> B
All the food she purchased within the past week ----> is in her refrigerator
C ----> B
Therefore, she purchased all the food in her apartment -----> within last week
A -----> C

Choice C:
All the food in Diane's apartment -----> is in her refrigerator
A -------> B
Diane purchased all the food in her refrigerator ----> within the past week
B -----> C
Therefore, she purchased all the food in her apartment -----> within the past week
A ------> C

My question is, would forming such a simplified, inaccurate diagram work for other parallel reasoning questions or would I have to be more precise? I don't want to get into a habit of using a method that won't help me get the correct answer in the future. Please advise.
Brook Miscoski
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Ataraxia,

I would remind all that there are multiple techniques one can use on parallel the reasoning. One is to diagram. Another is to recognize whether there is a prevailing concept at play. Another is to recognize whether the reasoning is good or bad. I do not believe that diagramming is necessary or even desirable to quickly answer this question correctly.

When I read through this stimulus, I see that the conclusion is correct because the store contains all of the mattresses, and they are all 20% off.

A. Bad reasoning. Fridge can have older food in it.
B. Bad reasoning. Doesn't show all food is in fridge.
C. Good reasoning and exact same verbal pattern.
D. Bad reasoning, she could have a snack out.
E. Bad reasoning, food older than a week could be in cupboard.

For distinguishing between A and C using your method, you needed to realize that the reversal of the second sentence is critical. If all the food in her fridge was purchased in the last week, that's parallel. If all the food purchased in the last week is in her fridge, there could also be older food in her fridge. Remember, ALL the mattresses were on sale.