On a certain village, each villager is either a human or a werewolf. Werewolves and humans . There are 4 villagers, Alice, John, Matt and Clarise. They each say the following:
: John is a werewolf.
: At most 2 of us are werewolves.
: John is human.
: Alice is human.
How many of them are human?
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I think its worthwhile telling you how I came up with this problem. The main part is testing the sentence uttered by John: at most 2 of us are human. There are two interesting aspects for this ("if true, this happens" vs "if false, this happens."). Let's start with Alice:
If Alice is human, then John lied. Notice that if what John said was true, then there would be 0, 1, or 2 werewolves but not 3 or 4. If we negate that, then among them are at least 3; that is, there are 3 or 4 werewolves. Another reason why I made this problem is because it sounds, at this point, too variable, meaning, which 3 could be werewolves? And what if its 4? But looking immediately at what Matt said, we know he lied. But Clarise didn't (look at how we started this whole thought experiment). This means that only John and Matt are werewolves, contrary to there being at least 3. Since this cannot happen, Alice cannot be saying the truth. Then she is a werewolf.
Since Alice is a werewolf, then John is human. Then there are at most 2 werewolves among them, John being one of them. But Matt told the truth also and that makes him the second human. Obviously, Clarise lied. Then there are 2 humans (and 2 werewolves). Try to answer this again but by assuming first that Alice is a werewolf and see how the thought process is different.