A puzzle about two brothers - tea lovers, which will help develop lateral thinking

2024 Author: Malcolm Clapton | [email protected]. Last modified: 2023-12-17 03:44

Try using one question to find out which of them you met.

This short logical problem was invented and sent to The Guardian by Chris Ovenden, a professor of philosophy at the University of Manchester. We have translated it so that you can also test your ingenuity. Can you find the right solution?

A scammer named Puzzi always drinks tea with two lumps of sugar and cannot lie. His brother prefers tea without sugar and cannot tell the truth.

One day you meet a man who is either Puzzi or his brother. You can ask him one question, to which he can only answer "yes" or "no." What do you ask to find out who is in front of you?

It's that simple! You need to ask a stranger what you know for certain. For example, ask him the question: "Is the sky blue?" If you hear an affirmative answer, then Puzzi is in front of you, and if you hear a negative answer, then his brother is a liar. The trick is that information about what tea the brothers prefer to drink is completely irrelevant for the decision.

The second option is to ask a question embedded within another question. For example: "If you were asked if you drink tea with sugar, would you answer in the affirmative?" Puzzi, who drinks sugar tea and doesn't lie, will say yes. A liar brother would answer “yes” to a direct question about whether he drinks tea with sugar. But since the question contains another question, he will have to lie a second time and he will answer “no”.

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