https://classic.7sage.com/lsat_explanations/lsat-b-section-2-game-2/

I have some questions about the proper diagram and meaning of a rule in this in/out game.

Rule 3: "If Yews are not in the park, then either L or O, but not both, are in the park."

- Could someone explain about how to properly diagram this rule (ideally in notation that does NOT involve biconditionals)? I diagrammed it as 2 separate rules (shown below), but I think it only confused me more...

/Y --> L or O (representing 'either/or')

/Y --> /L and /O (representing 'not both')

- If I'm understanding the meaning of this rule correctly, does the contrapositive of this rule basically mean/state that "if both L & O are in the park, then Y is in the park." ? Does the contrapositive of this rule also include "if both L & O are OUT, then Y is IN"?

TIA!

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1 comments

  • Thursday, Aug 25 2016

    I think JY diagrams it as /Y-->(/L(--)O)

    Alternatively you can diagram it as /Y-->(/O(--)L), which is the same exact thing, just showing the contrapositive of the embedded conditional.

    I like having the rule in one place as opposed to separate lines, because as soon as I see /Y I know I need to trigger the relationship in parantheses.

    If you're not comfortable with the biconditional you can also notate it as

    /Y-->L/O (where L/O is supposed to be whatever your notation is for "L and O are not together". For me I put them in a vertical box with a slash through, but I can't do that in this text box, so I typed them as L/O).

    And you are right, the contrapositive states that if you have both L and O in or both L and O out then Y has to be in.

    This might be one of the instances where it's worth writing down the contrapositive.

    I'd write it as

    LO -->Y where "LO" are supposed to be on vertically on top of each other and boxed to signify they are together.

    I hope that's clear enough.

    Essentially, Y out triggers L/O apart and LO together triggers Y in, however you want to notate it.

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