Which one of the following could be a complete and accurate list of the friends who appear together in a photograph?

Michael on May 28 at 05:10AM

The last rule confusion

I am confused on how to structure the last rule. The rule says “neither ty nor ramundo appear in any photograph that Wendy appears in”. Since the sentence seems like the previous rules (stating necessary first and then a sufficient condition) I want to set the rule up like this: W—-> not T & not R. However, the setup has it set up like this: T <—/—> W, R <—/—> W. How could you have known the setup wasn’t like a normal conjunction setup? Also, is the setup T <—/—> W like a normal sufficient/necessary setup where we can not know anything about the sufficient condition if the necessary condition is present? Thanks for your help!

2 Replies

Ben on May 28 at 06:20PM

Hi Mike, thanks for the question.

When I went through this game myself, I diagrammed the rule exactly as you did.

As you will see with LG, there often isn't a concretely right vs wrong method. The method used in the video is one such alternative. Showing the relationship between both variables and W.

<-/-> is used to show A -> Not B (in other words, they cannot occur together).

Considering when W occurs, both T and R do not, then it holds that neither T and W can occur together nor can R and W.

I would stick with your method if it feels right to you, both because you can take the contrapositive of your notation, as well as because it is intuitive to you.

Keep up the good work!

Michael on May 28 at 07:07PM

Thank you!