## #19 - Every student who walks to school goes home for lunch.

ellenb
LSAT Master

Posts: 261
Joined: Mon Oct 22, 2012 3:26 pm
Points: 0

Dear Powerscore,

I just want to make sure I have diagrammed the statements correctly for this question.

First Statement: WS->GHFL

Second Statement (conclusion): not WS some PTJ

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Also can we connect a statement such as A->B some C or we can connect only A some B->C which will be A some C? In this example if we put it all together, than we have,
PTJ some not GHFL --> not WS
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Conclusion: PTJ some not WS

Sort of like A some not B -->not C, A some not C.

Please let me know if I my diagrams seem to be correct.

Thanks

Ellen
Luke Haqq
PowerScore Staff

Posts: 183
Joined: Thu Apr 26, 2012 2:28 pm
Points: 143

Hi Ellen,

Your diagrams look good! And your intuition about the proper way to connect some statements with if-then statements is correct. Namely, from

A some B C

you can infer

A some C

However, you cannot make inferences if the form is instead,

A B some C
LSAT2018
LSAT Master

Posts: 247
Joined: Wed Jan 10, 2018 1:11 am
Points: 248

Can you confirm if this is right? The 'some' part gets me confused easily with the order

Walk to School → Home for Lunch
Not Home for Lunch → Not Walk to School
Part-time Jobs (Some) → Not Walk to School
Part-time Jobs (Some) → Not Home for Lunch → Not Walk to School
PowerScore Staff

Posts: 2680
Joined: Thu Apr 14, 2011 5:01 pm
Points: 2,493

Looks good, LSAT2018! Just keep in mind that the "some" arrow goes both ways, sort of like an "if and only if" situation. That is, if some A are B, that also means that some B must be A. In this case, if there are some students with part time jobs that do not go home for lunch, it also means that some people who do not go home for lunch have part time jobs (and there is your correct answer).

Nice work! If you happen to be enrolled in our Full Length course, you will find a module in the Online Student Center in Lesson 8 about Formal Logic - that's where we discuss diagramming things like "some" and "most". For now, remember that "some" means "at least one" and could mean all.
PowerScore LSAT, GRE, ACT and SAT Instructor
silent7706
LSAT Apprentice

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Joined: Tue Mar 26, 2019 9:59 pm
Points: 24

Hi,

P: WS GHFL
C: PTJ -WS
(D): PTJ -GHFL

I'm not seeing how some train travels backwards to connect with WS when GHFL is negated in (D). Can you please advise?

Brook Miscoski
PowerScore Staff

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Joined: Thu Sep 13, 2018 6:38 am
Points: 421

silent7706,

Write out the contrapositive of the premise:

-GHFL -WS

Now, consider (D), which states:

PTJ -GHFL

Those students (who are both PTJ and -GHFL) will not walk to school, because of the contrapositive.