Finding A Liar

Logic Level 1

Two identical twins can only be told apart by their behavior. Alvin always tells the truth, and Brandon always lies.

You walk over to their house and see them both leaning against the garage. One of the twins says, "As you know, my brother is a liar."

Which twin was speaking?

Alvin Brandon There is not enough information

1 solution

Denton Young
May 6, 2016

Relevant wiki: Truth-Tellers and Liars

The speaker could be Alvin: he would be telling the truth that Brandon is a liar.

Or the speaker could be Brandon: he would be lying about Alvin being a liar.

Moderator note:

Good clear explanation!

The first part gives it away: "As you know, ...". Since you don't know who is who at the beginning it must be the liar that spoke.

Dörthe Behrens - 5 years, 1 month ago

The twin is speaking to you. As explained in the solution, it could be either twin that spoke.

Calvin Lin Staff - 5 years, 1 month ago

He is making one more statement, 'As you know', which is false because we only know about the habit of A and B, but we don't know who is A and who is B. So he should be B.

J Chaturvedi - 5 years ago

The comment begins 'As you know...' This part of the statement is false so can only be spoken by Brandon.

Stephen Lissenden - 5 years ago

I also have the same solution. Since we know that one of them tells the truth and the other lies, we don't know who who said that.

Xylene resha terminio - 3 years, 7 months ago

“As you know” causes a lot of confusion… the question should be clearer

Diya Langalia - 3 weeks, 6 days ago

Finding A Liar

1 solution

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