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Rule contrapositives

General questions relating to the LSAT Logic Games.
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 ec623ec623
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-  Sun Mar 26, 2023 2:30 pm #100669
If there's a rule like 'G in 3rd only if Q is 5th' - I would diagram the rule as G3 -> Q5.

If I'm not mistaken, then doing the contrapositive it would be /Q5-> /G3. Does this mean if Q is not 5th, then G cannot be 3rd? Or just that G does not necessarily need to be 3rd (but is still able to be 3rd without Q being 5th)
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 Dave Killoran
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-  Mon Mar 27, 2023 11:04 am #100673
Hi EC,

Yes, well done, that's exactly what it means! The G3 -> Q5 relationship is incredibly powerful, and via the contrapositive, when Q is not in 5, then G has no chance of being in 3. That forces G into another spot aside from 3.

So, it's not that G is always in 3, but when it is, Q MUST be in 5.

Please let me know if that helps. Thanks!
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