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 andriana.caban
  • Posts: 143
  • Joined: Jun 23, 2017
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#71761
Hi!

I have a question on Chapter 3.

My question has to do with the Conditional Reasoning Diagramming exercise in the Logic Games Bible, question 7 on page 72.

I diagrammed it as follows:

Please note that my use of bracket ([ ]) was to replicate the block over two variables.

[KG] :arrow: [FKG]
[FKG] :arrow: [KG]

But the answer located on page (75) shows the following relationship as the contrapositive for the first conditional I diagrammed:
[FK] :arrow: [KG]

Why is it only [FK] :arrow: [KG] and not what I diagrammed?
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 Dave Killoran
PowerScore Staff
  • PowerScore Staff
  • Posts: 4235
  • Joined: Mar 25, 2011
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#72023
Hi Andriana,

It's because the FKG was a result of the sufficient conditional occurring in the first example. Technically the rule is KG :arrow: FK. But, if we know the sufficient condition happens (KG), we can add it to that necessary condition to show the complete result when KG happens (so, not just FK but FKG). However, in the contrapositive, the condition being negated is just FK; it doesn't have to be all of FKG.

Thanks!

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