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Heather's Fiancé (Posted on 2023-02-22) Difficulty: 3 of 5
Heather is engaged to either Abe, Brad, Cody, or Dean. Each of the four men plus Heather is either a Knight, who always tells the truth or a Liar, who always speaks falsely.
Their statements are as follows:
  • Abe says, "Exactly one of us four men always tells the truth".
  • Brad says, "Exactly one of us four men always lies".
  • Cody says, "Heather's fiancé is either Abe or Brad."
  • Heather says, "My fiancé and I either always tell the truth or always lie".
Who is Heather's fiancé? What are the types of the five individuals?

See The Solution Submitted by K Sengupta    
Rating: 5.0000 (1 votes)

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most of the solution | Comment 1 of 2
From H's statement, her fiance always tells the truth.

If A is the sole truth teller, he's the fiance and C is telling the truth --  a contradiction. So A is a liar.

If B is telling the truth, then so is C and D is also a truth teller. H's fiance would then be Brad. This would seem to be a possible solution for the men.

What if B were telling a lie? At least 2, A and B, would be liars. We know that it can't be 3 men that are liars so C and D would need to be both liars or both knights. But C can't be a knight as neither A nor B is the fiance, so both are liars, but that leaves no knight left to be H's fiance, so this is not the case.

So B, C and D are all knights. A is a liar and B is H's fiance.

I can't tell the veracity of Heather.

  Posted by Charlie on 2023-02-22 10:34:55
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