PT20.S4.Q15 - rhonda will see the movie tomorrow

Nanchito-1-1

http://7sage.com/lsat_explanations/lsat-20-section-4-question-15/
Someone please explain.

Pacifico

So this is a fairly straightforward A --> B --> C, /C therefore /A stimulus disguised with some group two and three indicators. The stimulus breaks it down as A --> B, B --> C, /C therefore /A which is just asking you to chain up the A,B,C relationship through the transitive property and then run the contrapositive back to negate A.

Answer Choice A starts off with a A --> /B statement and then says A --> C so you can get rid of that pretty quickly.

Answer Choice B is what you're looking for as it gives you the same A --> B, B --> C, /C therefore /A structure.

Since it's a pretty straightforward reasoning structure, during a timed test it would behoove you to stop right there and circle B, bubble it in and move on since a quick diagram should really make you 100% confident on this question.

This is a great question to practice diagramming since it has a couple different logical indicator groups to translate, as well as necessitating the use of the contrapositive. After attempting questions like these I think it is very helpful to go ahead and diagram every AC in order to get in some good practice. PR and PF questions and their ACs are usually a gold mine for this. Go ahead and see if you can diagram ACs C, D, and E and post them here if you like and you can tell us why each one of those is wrong.

If you're having issues with some of the concepts I discussed I would refer back to these lessons and the ones around them:

http://7sage.com/lesson/4-translation-groups-cheatsheet/

http://7sage.com/lesson/chaining-conditional-statements-together/

Hope that helps, let me know if you have any other questions.

Nanchito-1-1

Thanks @Pacifico i did not contrapose the second statement which pressed me to just pick e under timed conditions and no matches to my initial chain of a->b, /c->/b therefore /c->/a.

for c: /a->b, /b->/c, /c so /a
for d:a->b or c, b so a
for e:/a ->/b, a->c,c so a

Pacifico

No problem, happy to help! Just remember that when you do decide to diagram, you need to do your best to try to chain up anything and everything that you can, whether it's during LG or LR. For questions like this one, everything will chain nicely and the correct AC will mirror that. For conditional heavy SA questions, there will just be that one chain missing and that will be the correct AC, just make sure you've got the sufficiency/necessity relationship correct.

TheLSAT_CAT

This is an interesting question! I actually answered this correctly and I thought I had it but when I saw the explanations they're saying it's a A(Ronda goes)> B(Paul goes)> C (Ted goes) that strikes me as strange! I saw unless, so I negated the sufficient and got (Ted doesn't go)>(Paul won't go) therefore Ronda won't go, which led me to the correct answer choice. My problem is that the A>B>C relationship, doesn't that essentially say B (Paul going) is sufficient for Ted to go, which isn't what the stimulus is saying?

hlsat180

@ojokelvin22 said:
My problem is that the A>B>C relationship, doesn't that essentially say B (Paul going) is sufficient for Ted to go, which isn't what the stimulus is saying?

It's not clear to me what you are asking but here's a guess at it. The stimulus logic chain ( R --> P --> T ) and its contrapositive ( ~T --> ~P --> ~R) both "state" the same relationships - just in two different ways.