Humans and Werewolves Part3

Logic Level 1

On a certain village, each villager is either a human or a werewolf. Werewolves always lie \textbf{always lie} and humans always tell the truth \textbf{always tell the truth} . There are 4 villagers, Alice, John, Matt and Clarise. They each say the following:

Alice \textbf{Alice} : John is a werewolf.

John \textbf{John} : At most 2 of us are werewolves.

Matt \textbf{Matt} : John is human.

Clarise \textbf{Clarise} : Alice is human.

How many of them are human?


The answer is 2.

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4 solutions

Jay B
Jan 24, 2019

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 \textbf{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.

Alice and Matt have opposite statements so one of them is lying. We find out who is lying with John’s statement. John says “at most two of us are werewolf’s.”

So let’s say we believe Alice is telling the truth that means that John is a werewolf and that Matt is also a werewolf for lying. So far we have 2 wolves, but Clarise is a human because she says Alice is human, because Alice is human John is lying, but John the werewolf isn’t lying! This is because of his statement (“at most two of us are werewolves”) is true since only two people are wolfs, but were-wolves can only lie making this choice impossible.

Now we look at it again with Matt as a Human. If what Matt says is true, then Alice is lying as well as John telling a truth. This then leaves Clarise. Since Alice is a Wolf Clarise is lying making themself a wolf as well. Making the village have 2 humans.

We can only find this because John’s statement will always be true whether he is human or a wolf, since a wolf cannot tell the truth then John cannot be a wolf. Figuring that out will also find the identities of the other villagers.

TL;DR: since two people point out John, one of them is lying. So if John’s statement is true then there are 2 humans. John’s statement is always true. Making the village have two humans.

A Former Brilliant Member - 2 years, 4 months ago
Jebin George
Apr 6, 2020

There is two groups group a and group b..

Alice is going to group A Matt is going to group B

Since both of there statement is contradictory..

Now clarise will go to group A bcz if Alice is actually a human the Clarise is also a human if not clarise also is not a human..

So as of now Alice & Clarise is group A And matt is group B..

Now comes john..

Since alice told jhon is a ware wolf jhon will be always on the other group bcz if alice is werewolf jhon is human. If alice is human then her sattement is correct and john is werewolf.... Any way john is now in group B.

Now both group has 2 each members . And it doesn't matter which group is werewolf bcz.. nhmber of werewolf is 2..

Winston Choo
Jan 24, 2019

Note that between Alice and John only one of them is human, based on Alice's statement about John.

Now note that between Matt and Clarise only one of them is human, based on what they've said about Alice and John.

We now realise John's statement is actually not needed to solve this problem! There are 2 humans within the 4 people.

Hence, the answer is 2 humans. Easy solution??

John’s statement is also important as well! If he said something that can was a lie for example “all of us are wolves” then there would be 3 wolves instead of 2. We can only solve this due to John’s statement being true.

A Former Brilliant Member - 2 years, 4 months ago

But John's statement might not be true, and this would still result in 2 werewolves.

Winston Choo - 2 years, 3 months ago

2 confusing

the cool congle - 1 year, 11 months ago

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