Q25 - Some visitors to the park

[mrudula_2005]

Can you help me understand what makes E a bad answer?

I did choose C but I see E as following the same structure, especially if the second sentence is understood in this form (bolded): Some members of the Liberal Party are in favor of the proposed ordinance. But all members of the city council are opposed to the proposed ordinance (But no one on the city council is in favor of the proposed ordinance). Hence some members of the city council are not Liberals.

is it because the last sentence has it switched around? should it be "Hence some members of the Liberal Party are not members of the city council" ?

I'm a little confused here in trying to figure out what makes E wrong and what would make it right. Thanks

[sgorginian]

Here's how I worked the problem, hopefully this helps. =)

I'm using caps, to help myself. Plus incorrect grammar is intentional.

SOME visitors harm animals. But, NONE visitor would do these practices if they knew it was harmful. So, at least SOME of those visitors who harmed did not know they were harming.

So basically, the original pattern is SOME-NONE-SOME

(A) SOME who worked on project will be fired. ALL played a role. Therefore, SOME will be fired.

Not matching original pattern Some-None-Some. This answer is Some-ALL-Some. Eliminate it....

(B) SOME who signed petition were supporters. MAYOR denounced everyone. So, SOME supporters were denounced.

This answer is Some-Mayor-Some or Some-Everyone-Some does not match with original pattern. Eliminate it....

(D) ALL planners responsible. NONE will admit responsibility. So, SOME will not admit responsibility.

This is ALL-NONE-SOME, and doesn't match our original Some-None-Some. Eliminate it....

(E) SOME Liberal Party members favor ordinance. ALL city council members oppose. So, SOME city council members are not liberals.

This answers pattern is Some-All-Some which does not match our original Some-None-Some. Eliminate it....

(C) SOME live outside city limits. NONE who vote live lives outside city. So, SOME cannot vote in city elections.

Perfect match! Some-None-Some in answer matches with original Some-None-Some!!!


I hope that helped!
Sevan

[ManhattanPrepLSAT1]

Good work so far both of you.

mrudula_2005 wrote:

is it because the last sentence has it switched around? should it be "Hence some members of the Liberal Party are not members of the city council" ?

This is the correct reason why answer choice (E) is incorrect! Good work.

Let me take a second though and run through some of the other answer choices as well.

Here's the reasoning in the stimulus. (Notation Key: VP = visitors to the park, H = harm animals, K = know)

VP some H
K ---> ~H
=======
VP some ~K

This is a valid argument and the reasoning relies on the application of a contrapositive to the second premise.

(A) (Notation Key: WP = worked on the project, F = fired, D = in the department)

WP some F
D ---> WP
=======
D some F

This is not a valid argument; no conclusion can be drawn from those premises. So this answer choice does not match the reasoning in the stimulus.

(B) (Notation Key: SP = signed the petition, MS = mayor's supporters, D = denounced)

SP some MS
SP ---> D
=======
MS some D

This is a valid argument and is fairly close in structure. If answer choice (C) were not present, this would be a viable answer choice. The problem here is that it does not rely on a contrapositive.

(C) (Notation Key: P = polled, LO = live outside the city, V = vote)

P some LO
V ---> ~LO
=======
P some ~V

This is a valid argument using the same reasoning and relies on a contrapositve. Thus, the correct answer.

(D) as sgorginian wrote:

This is ALL-NONE-SOME, and doesn't match our original Some-None-Some. Eliminate it....

(E) (Notation Key: LP = liberal party, FO = in favor of ordinance, CC = city council)

LP some FO
CC ---> ~FO
=======
CC some ~LP

This is not a valid argument. The conclusion should have been
LP some ~CC. Close but not quite!

I hope this helps... If anyone sees something else, I'd love to hear it.

[zainrizvi]

Formal logic parallel Qs tend to slow me down the most. Is there any alternative strategy, other than just diagramming what's going on?

[ManhattanPrepLSAT1]

Sure, there are plenty of top-scorers out there who don't use notation on the questions that test conditional logic. The issue is that without notation, you're relying on your intuition to lead you to the correct answer. Sometimes you can identify structures that do not need to be notated, but that could be used to help make eliminations - such as either/or statements, quantifications, recommendations, etc.

But if you don't see those to help you with the eliminations, for me, i need to use the notation, or I can't find the difference between the answer choices.

For this question, I'd need to use the notation.

[jamiejames]

Good work so far both of you.

mrudula_2005 wrote:

is it because the last sentence has it switched around? should it be "Hence some members of the Liberal Party are not members of the city council" ?

This is the correct reason why answer choice (E) is incorrect! Good work.

Let me take a second though and run through some of the other answer choices as well.

Here's the reasoning in the stimulus. (Notation Key: VP = visitors to the park, H = harm animals, K = know)

VP some H
K ---> ~H
=======
VP some ~K

This is a valid argument and the reasoning relies on the application of a contrapositive to the second premise.

(A) (Notation Key: WP = worked on the project, F = fired, D = in the department)

WP some F
D ---> WP
=======
D some F

This is not a valid argument; no conclusion can be drawn from those premises. So this answer choice does not match the reasoning in the stimulus.

(B) (Notation Key: SP = signed the petition, MS = mayor's supporters, D = denounced)

SP some MS
SP ---> D
=======
MS some D

This is a valid argument and is fairly close in structure. If answer choice (C) were not present, this would be a viable answer choice. The problem here is that it does not rely on a contrapositive.

(C) (Notation Key: P = polled, LO = live outside the city, V = vote)

P some LO
V ---> ~LO
=======
P some ~V

This is a valid argument using the same reasoning and relies on a contrapositve. Thus, the correct answer.

(D) as sgorginian wrote:

This is ALL-NONE-SOME, and doesn't match our original Some-None-Some. Eliminate it....

(E) (Notation Key: LP = liberal party, FO = in favor of ordinance, CC = city council)

LP some FO
CC ---> ~FO
=======
CC some ~LP

This is not a valid argument. The conclusion should have been
LP some ~CC. Close but not quite!

I hope this helps... If anyone sees something else, I'd love to hear it.

With your conditional logic for C, "V ---> ~LO" I'm having some trouble getting the V --> ~LO the right way around. This is just something I need to get down once, and then I'll be able to apply it to every in the future.

So, "No one who can vote in city elections lives outside the city"

Is the same as saying "if you vote, you can't live outside the city," right?
___
Also, with "VP some H"

why would it not be " some VP --> H"?

[timmydoeslsat]

With your conditional logic for C, "V ---> ~LO" I'm having some trouble getting the V --> ~LO the right way around. This is just something I need to get down once, and then I'll be able to apply it to every in the future.

So, "No one who can vote in city elections lives outside the city"

Is the same as saying "if you vote, you can't live outside the city," right?
___
Also, with "VP some H"

why would it not be " some VP --> H"?

Vote in CE ---> ~LOC

LOC ---> ~Vote in CE

You are correct on that conditional.

With the some statement of VP some H, it is a very prudent thing to do with quantifying statements, as it shows a distinction between quantifying language and conditional language.

The argument in the stimulus:

V some E

Knew ---> ~E
____________
V some ~Knew

This is one of the few questions I have ever seen that has answer choices using valid forms of reasoning, one with the contrapositive and one not. So to truly match the pattern of reasoning, the use of the contrapositive would be an aspect to keep in mind. Generally, however, this much detail in reasoning is not tested. I am sure a lot of test takers went with B before even checking C.

[maria487]

(E) (Notation Key: LP = liberal party, FO = in favor of ordinance, CC = city council)

LP some FO
CC ---> ~FO
=======
CC some ~LP

This is not a valid argument. The conclusion should have been
LP some ~CC. Close but not quite!

I hope this helps... If anyone sees something else, I'd love to hear it.[/quote]



Aren't "some" statement flexible? Can't the conclusion be read both as "some CC are ~LP" and also as "some ~LP are CC"? When you reverse the order of the conclusion to "~LP some CC," it matches the structure of the stimulus. I went with C because it did not require you to do this, but I just wanted to know if my reasoning is valid.

[ManhattanPrepLSAT1]

Aren't "some" statement flexible? Can't the conclusion be read both as "some CC are ~LP" and also as "some ~LP are CC"? When you reverse the order of the conclusion to "~LP some CC," it matches the structure of the stimulus. I went with C because it did not require you to do this, but I just wanted to know if my reasoning is valid.

You are right that "some" statements are reversible. However, that doesn't mean that answer choice (E) matches the structure of the stimulus. Note that the stimulus is a valid argument, while answer choice (E) is an invalid argument. For answer choice (E) to match it should have concluded that some members of the Liberal party are not members of the city council.

Good one!

Often on Match the Reasoning or Match the Flaw questions, we find that two answers look very close to reasoning structure in the stimulus, but if you check the validity of the argument, you'll find that one doesn't match. So ... check structure first, and finish with checking the argument's validity!

[maria487]

Aren't "some" statement flexible? Can't the conclusion be read both as "some CC are ~LP" and also as "some ~LP are CC"? When you reverse the order of the conclusion to "~LP some CC," it matches the structure of the stimulus. I went with C because it did not require you to do this, but I just wanted to know if my reasoning is valid.

You are right that "some" statements are reversible. However, that doesn't mean that answer choice (E) matches the structure of the stimulus. Note that the stimulus is a valid argument, while answer choice (E) is an invalid argument. For answer choice (E) to match it should have concluded that some members of the Liberal party are not members of the city council.

Good one!

Often on Match the Reasoning or Match the Flaw questions, we find that two answers look very close to reasoning structure in the stimulus, but if you check the validity of the argument, you'll find that one doesn't match. So ... check structure first, and finish with checking the argument's validity!

Wow, for the life of me, I couldn't see that the negation of E's conclusion was reversed until I just revisited it.

So then, (E) is wrong because it concludes "CC some ~LP." To be the correct answer, it needed to conclude "LP some ~CC."

Thank you for your helpful explanation!