If both martins and harriers are in the forest, then which one of the following must be true?

McLean on June 15, 2021

I'm confused on how to properly conclude that anything other than M and H are in the forest.

Hi, I'm still a little confused on this question, the contrapositive of rule 3 states Not G --> Not W, but since we only know that we don't have G how can we invoke that necessary condition to mean that we don't have W as well? Wouldn't that be working backwards?

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Emil-Kunkin on November 22, 2023

We aren't invoking the necessary. We know that g is out, so that invokes the sufficient, if not g, therefore the necessary must be true as well, that not w.