## Eliminating answer choices with logic

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ebb44

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### Eliminating answer choices with logic

Has anyone ever come across questions where some answer choices can be eliminated using only logic based on text within the question and choices and NOT specific information about rules in logic games or text from LR stimuli?

For example if you have a could be true question in LG where you have two logical opposites in the answer choices, then the answer must be one of them (e.g. H is in 1 and H is not in 1).
Last edited by ebb44 on Mon Feb 20, 2012 5:03 pm, edited 2 times in total.

gaud

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### Re: Eliminating answer choices with pure logic

I'm confused... I thought using logic was how most of the questions on the test are supposed to be answered? (Logic games, logical reasoning)

20130312

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### Re: Eliminating answer choices with pure logic

Yes, I use logic all the time in the logic games and logical reasoning sections.

gaud

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### Re: Eliminating answer choices with pure logic

InGoodFaith wrote:Yes, I use logic all the time in the logic games and logical reasoning sections.

Glad we're on the same page.

20130312

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### Re: Eliminating answer choices with pure logic

gaud wrote:
InGoodFaith wrote:Yes, I use logic all the time in the logic games and logical reasoning sections.

Glad we're on the same page.

Ah, guess you beat me to it. But yeah, not really sure what this thread set out to accomplish?

kwais

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### Re: Eliminating answer choices with pure logic

InGoodFaith wrote:Yes, I use logic all the time in the logic games and logical reasoning sections.

gaud

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### Re: Eliminating answer choices with pure logic

InGoodFaith wrote:
gaud wrote:
InGoodFaith wrote:Yes, I use logic all the time in the logic games and logical reasoning sections.

Glad we're on the same page.

Ah, guess you beat me to it. But yeah, not really sure what this thread set out to accomplish?

Whenever I ask myself a question of this sort I use my logic to determine TCR is always:

troll (regardless of whether or not it's true)

ebb44

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### Re: Eliminating answer choices with pure logic

Ok, I'll try to clarify what I meant because it looks like there is some confusion. In the example I gave I was able to eliminate answer choices without even looking at the rules of the logic game. I can look at that question, see that it's a could be true question with two logically opposite answers in the choices, and eliminate 3 out of 5 choices on that basis. I don't have to read anything outside of the text of the question and choices to eliminate those 3 choices.

20130312

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### Re: Eliminating answer choices with pure logic

I have also done that before.

Kabuo

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### Re: Eliminating answer choices with pure logic

ebb44 wrote:Ok, I'll try to clarify what I meant because it looks like there is some confusion. In the example I gave I was able to eliminate answer choices without even looking at the rules of the logic game. I can look at that question, see that it's a could be true question with two logically opposite answers in the choices, and eliminate 3 out of 5 choices on that basis. I don't have to read anything outside of the text of the question and choices to eliminate those 3 choices.

You should probably patent that and look into teaching.

062914123

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### Re: Eliminating answer choices with pure logic

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Last edited by 062914123 on Sun Jun 29, 2014 7:47 pm, edited 1 time in total.

20130312

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### Re: Eliminating answer choices with pure logic

bee wrote:
ebb44 wrote:Ok, I'll try to clarify what I meant because it looks like there is some confusion. In the example I gave I was able to eliminate answer choices without even looking at the rules of the logic game. I can look at that question, see that it's a could be true question with two logically opposite answers in the choices, and eliminate 3 out of 5 choices on that basis. I don't have to read anything outside of the text of the question and choices to eliminate those 3 choices.

Wait... what if both logically opposite choices are incorrect? Am I missing something here?

For a could be true question, if there are logical opposites, then it must follow that one of the two is a correct answer.

062914123

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### Re: Eliminating answer choices with pure logic

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Last edited by 062914123 on Sun Jun 29, 2014 7:47 pm, edited 1 time in total.

Mr.Binks

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### Re: Eliminating answer choices with pure logic

InGoodFaith wrote:
bee wrote:
ebb44 wrote:Ok, I'll try to clarify what I meant because it looks like there is some confusion. In the example I gave I was able to eliminate answer choices without even looking at the rules of the logic game. I can look at that question, see that it's a could be true question with two logically opposite answers in the choices, and eliminate 3 out of 5 choices on that basis. I don't have to read anything outside of the text of the question and choices to eliminate those 3 choices.

Wait... what if both logically opposite choices are incorrect? Am I missing something here?

For a could be true question, if there are logical opposites, then it must follow that one of the two is a correct answer.

Makes sense. How often does this happen? I don't recall ever coming across one. Maybe I have, but just missed that deduction.

Kurst

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### Re: Eliminating answer choices with pure logic

This happens frequently in logic games. If variables X and Y are functionally identical in a game (i.e. no rule applies to them that does not apply to every other variable), and you have a question such as:

Which of the following must be included?

(A) George
(B) John
(C) Alexander
(D) X
(E) Z

...then you know that answers (D) and (E) are incorrect, for if either of them were correct, the other would also be correct -- but no LSAT question can have two correct answers.

LSAT Blog

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### Re: Eliminating answer choices with pure logic

An example of this style of thinking (in a must be true LG question) is in PT33, G2 (the birds in the forest game), Q11. One can eliminate C simply due to the fact that if C were true, then both A and B would have to be true as well, and a question cannot have 3 correct answers.

Mal Reynolds

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### Re: Eliminating answer choices with pure logic

I like eliminating answers with impure logic.

ebb44

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### Re: Eliminating answer choices with pure logic

Mal Reynolds wrote:I like eliminating answers with impure logic.

There are different types of logic. The study of logic can be split into two categories: applied logic and pure logic. I guess pure logic isn't the right word to use in this case.

20130312

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### Re: Eliminating answer choices with pure logic

ebb44 wrote:
Mal Reynolds wrote:I like eliminating answers with impure logic.

There are different types of logic. The study of logic can be split into two categories: applied logic and pure logic. I guess pure logic isn't the right word to use in this case.

Oh God, tell me you're a philosophy major.

bp shinners

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### Re: Eliminating answer choices with logic

My personal favorites are the LR flaw questions that provide answers that aren't actually flaws (and they usually end up getting about 30% of people). One question explained the logic behind the contrapositive in such an obscure way that I think more people picked it than the right answer.

suspicious android

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### Re: Eliminating answer choices with logic

Happens quite frequently on LG as pointed out above, the best examples I can think of off hand is the game with three subcommittees, Pinsky and Msomething, F, G, H and I. Variables P and M were the only ones that could be on every subcommittee, and one of them had to, but they were no real difference between the two variables. Same with F and G, also with H and I. Recognizing this makes the game go from quite difficult to almost childishly simple, you end up being able to eliminate bunches of answer choices based on this idea.

On LR, it's pretty frequent on flaw quesitons, as BP pointed out. Another way you can sometimes eliminate answer choices comes up on occasion on role in the argument questions. I can't remember where this occured or the precise wording, but there was a question once that asked to describe the role of a particular statement as either:

A: a premise of the argument
B: an intermediate conclusion of the argument

Well, even if you couldn't even understand a single word of the stimulus, you'd be able to eliminate answer choice B, since intermediate conclusions function both as premises and conclusions. If B were correct, A would also be correct as well. That's no good. A could theoretically be correct if the statement was asserted without any support, but if I recall correctly, neither of those two answer choices were correct on that question and my students were bored as I explained the logical details of two incorrect answers.

Mal Reynolds

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### Re: Eliminating answer choices with pure logic

Mal Reynolds wrote:I like eliminating answers with impure logic.

You changed the OP damn you. Now I look like an idiot. You never make Captain Reynolds look like an idiot.

AriGoldButNicer

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### Re: Eliminating answer choices with logic

I hear what op is saying. The lsat is configured in a way that you can break down most sentences into two parts.... Like most winters are cold can be if its winter it's probs cold, but when a choice says it's cold so its probs winter (flippin da logic) it's always off base. However, u really gtta see it naturally all the time like a reflex or your timing will be off. Once i got thiss down i went from -3 to -5 in each lr to minus 0 to minus 1. I found it was the best technique i had, and most reliable.

MLBrandow

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### Re: Eliminating answer choices with logic

ebb44,

At least for logic games, generally I find it helpful when looking at EXCEPT questions to immediately gravitate toward the following:

"Each of the following must be true EXCEPT:" - Look for an answer choice containing the least restricted variable.

"Each of the following could be true EXCEPT:" - Look for an answer choice containing the most restricted variable.

Often it's best to just take your time, apply the rules and do a hypothetical if you need to. But if you feel pressed, I find both of these insights generally helpful, if not slightly intuitive.

Now, as for logical reasoning questions, I can offer some grain of insight that might help you in a pinch.

A test-maker is going to almost always prefer to bait you into picking the wrong answer choice. There are a number of ways to bait you into doing it, but one of the tried and tested ways (and the most common to see on the LSAT) is that of seeing the best trap answer immediately precede the correct answer choice. This happens much more often than you might think. The order of the answer choices is NOT random, and knowing this can give you an advantage if you're in a bind and are truly stumped on the answer.

Further, nearly every question contains at least one or two answer choices that are just garbage--they have nothing to do with the stimulus in cases where you can only use information from the stimulus, or they just don't impact the argument in any way. Anyway, these answers are, by and large, easy for most people to rule out. Think of this not as the test-makers being lazy and failing to come up with four good, wrong answer choices; instead see it as the test-maker attempting to lure you into a more attractive, but still incorrect, answer choice.

Let me give you an example. Consider the following necessary assumption question I actually wrote myself (if you can believe that):

=====================
Blah blah blah stimulus thing.

Which somethingrather assumption argument depends?

A. something obvious, mentioned in the stimulus that must be true but isn't necessary.
B. garbage
C. garbage
D. clever trap involving material from the stimulus applied in an odd and slightly cumbersome way.
E. credited response
================

Here's another common layout:

================
Blah blah blah stimulus thing.

somethingsomething must be true?

A. cryptically written credited response
B. garbage
C. garbage
D. garbage
E. clever trap involving material from the stimulus applied in an odd and slightly cumbersome way
==========

If you ever find yourself crossing out garbage immediately before an attractive answer choice, RECONSIDER. That clever trap is going to be MUCH more attractive than the garbage answers, and the author of the question knows that.

Imagine being in a bar and you walk in and pass by some chick at a table looking down on her cell phone and seemingly uninterested. Then, you see three women with eye patches and psoriasis accompanying a woman of average looks. After being hit on by each of these three Pirate McScruffingtons, suddenly the average woman catches your eye, she seems into you, and then you buy her a drink which she casually accepts. You're thinking the whole time this couldn't have been any easier, but what you didn't realize is that these four women are gypsies, and this is a con, while the woman on her cell phone got stood up by her idiot boyfriend and is actually a former Miss North Dakota with a PhD in biochemistry and while we're at it, some great legs, too.

The point is that if you were fully assertive, you'd have probably noticed Dr. Miss North Dakota even if it was only a glancing pass. But when you go to the bar to meet a woman, you don't stop at the first one who looks alright and gives you some attention, and you should at least raise an eyelash to why this otherwise alright woman is hanging around so seemingly out of her element.

That gypsy is out to get your money and possibly harvest your organs--and the wrong LSAT answer choices are out to steal your LSAT points.

Anyway, the moral of the story is that if you're pressed for time, you probably will pick an answer that's better than the other ones, but be wary of being steered toward a trap answer. I call this "the law of traps" although it's really more a theory than some immutable truth. Still, I've had tremendous success applying it to some questions, and it can really help clear things up when you have to pick a choice and move on.

Good luck and study hard!

lovejopd

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