Q13

[hilarykustoff]

I keep going down the list of constraints, but for some reason it isn't working for me. Thanks for your help!

[timmydoeslsat]

I keep going down the list of constraints, but for some reason it isn't working for me. Thanks for your help!

This is a global question stem asking for a single valid hypothetical.

You are right in that we want to apply our rules one at a time and go through all 5 answer choices with that rule, and continue on in the same way with the other rules.

A) Violates the W --->~T and ~R

B) Does not violate any rules = correct answer

C) Violates the W ---> ~T and ~R

D) Violates the S ---> W

E) Violates the ~Y ---> R

[hilarykustoff]

Why does B not violate -y-->r?? You can't have both of them right?

[timmydoeslsat]

Why does B not violate -y-->r?? You can't have both of them right?

The ~Y --->R rule is a rule that signifies at least one one must be present.

Could you ever have both Y and R out? No. The moment one of those variables is out, the other must be in.

Could you ever have both Y and R in? Sure.

If I have Y in...this rule does not apply.

If I have R in...this rule does not apply.


You would be correct in your thinking with the rule of: Y --->~R

That is a rule that signifies not both.

[hilarykustoff]

That makes sense! Thanks!

[mcarmody]

Why does B not violate -y-->r?? You can't have both of them right?

The ~Y --->R rule is a rule that signifies at least one one must be present.

Could you ever have both Y and R out? No. The moment one of those variables is out, the other must be in.

Could you ever have both Y and R in? Sure.

If I have Y in...this rule does not apply.

If I have R in...this rule does not apply.


You would be correct in your thinking with the rule of: Y --->~R

That is a rule that signifies not both.

I'm still confused as to why the contrapositive doesn't stand in this case. R --> -Y would be Y--->-R
Is it the language of the constraint because it doesn't specifically leave out the possibility that they can both be in the same picture?

[ManhattanPrepLSAT1]

I'm still confused as to why the contrapositive doesn't stand in this case. R --> -Y would be Y--->-R
Is it the language of the constraint because it doesn't specifically leave out the possibility that they can both be in the same picture?

Remember the rule is ~Y ---> R, so the contrapositive would be ~R ---> Y.

A rule that goes from negative to positive is saying that at least one of the two must be in the photograph, leaving open the possibility that they are both in the photograph. The only thing that cannot occur with Y and R according to this constraint is that they are both NOT in the photograph.

Hope that helps!

[solomon.waller]

How come (B) doesnt violate the third rule?

[stacksdoe]

How come (B) doesnt violate the third rule?

thats already been covered: R and Y can appear together, the only thing that cannot happen between R and Y is that they are both excluded from the photograph. Thus no matter the scenario, one of R and Y, or both, must appear.