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Photo: Michael Niestedt / DER SPIEGEL
Some always lie, others always tell the truth.
This rarely happens in real life, but in the world of logic puzzles it is almost normal.
As in the following exercise, which comes from my new book "Blind Date with Two Strangers".
Three women are sitting in a café.
Each of them is either a notorious liar or loves the truth about everything.
The waiter wants to find out how many liars there are among them.
He asks each of the three women the same question: "Are you a liar or a friend of the truth?"
The first woman answers, but so quietly that the waiter cannot understand her.
The second says: “My neighbor said she was always telling the truth.
This is true.
And I always tell the truth too. "
The third explains: “I always tell the truth.
But the other two are liars. "
The waiter is at a loss.
Especially since it has now become clear to him that his question was not well chosen.
Can you help him find out who is who?
The third woman is a liar, the other two are telling the truth.
When asked by the waiter, liars and those who love the truth give the same answer: "I always tell the truth."
In this respect, the question was actually not well chosen.
Nevertheless, the constellation can be clarified.
The waiter did not understand the first woman's answer, but the second woman repeated it for him: "My neighbor said she always told the truth."
We know this is a true statement whether the first woman lies or not.
Your answer must always be: "I am telling the truth." The second woman is therefore telling the truth and cannot be a liar.
Because the second woman also declares that the first woman's statement is true, it follows that the first woman is also not a liar.
But the third woman.
Because she calls her two neighbors liars, which is definitely wrong.
If you missed a puzzle from the past few weeks, here are the ten most recent episodes:
How does the sequence of numbers continue?
The round is in the square
The magic number triangle
Built on a gap
The racing bike clique
A king on the run
The carpet repair
Brand diversity at Swiss Post
Is Dieter the thief?
One circle, two points
