Hats off to you prince!

Logic Level 2

A king wants his daughter to marry the smartest of 3 extremely intelligent young princes, and so the king's wise men devised an intelligence test.

The princes are gathered into a room and seated, facing one another, and are shown 2 black hats and 3 white hats. They are blindfolded, and 1 hat is placed on each of their heads, with the remaining hats hidden in a different room.

The king tells them that the first prince to deduce the color of his hat without removing it or looking at it will marry his daughter. A wrong guess will mean death. The blindfolds are then removed.

You are one of the princes. You see 2 white hats on the other prince's heads. After some time you realize that the other prince's are unable to deduce the color of their hat, or are unwilling to guess. What color is your hat?

Note: You know that your competitors are very intelligent and want nothing more than to marry the princess. You also know that the king is a man of his word, and he has said that the test is a fair test of intelligence and bravery.

White hat Insufficient information Black hat

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5 solutions

The king would not select two white hats and one black hat. This would mean two princes would see one black hat and one white hat. You would be at a disadvantage if you were the only prince wearing a black hat.

If you were wearing the black hat, it would not take long for one of the other princes to deduce he was wearing a white hat.

If an intelligent prince saw a white hat and a black hat, he would eventually realize that the king would never select two black hats and one white hat. Any prince seeing two black hats would instantly know he was wearing a white hat. Therefore if a prince can see one black hat, he can work out he is wearing white.

Therefore the only fair test is for all three princes to be wearing white hats. After waiting some time just to be sure, you can safely assert you are wearing a white hat.

2 options 3 attempts.

Archit Boobna - 6 years ago

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yeah thats why i was asking can we change the solution of the question....I did a mistake while writing the solution, actually i was thinking about MCQ.

Can we edit the answer of the question?

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I've implemented the MCQ format for this question.

Brilliant Mathematics Staff - 6 years ago

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Thank you so much

It was given that the competitors are intelligent. Then why didn't the others figure it out first ,since they all have the same situation ?

Abin Das - 5 years, 11 months ago
Simon Boutin
Jun 14, 2015

You are prince A. I you wear a black hat, prince B sees that C can't deduce, so B should know he wears a white hat. But here he doesn't. So you wear a WHITE hat

Jerry Keith
Jul 9, 2015

The king said it was a fair test and the only way for it to be fair is if they are all wearing white hats.

Joseph Andrade
Jul 5, 2015

Without loss of generality, call one prince A and the other B (no loss of generality since they both have the same view: a white hat and your hat, and because they both have the same color hat). If you have a black hat, A would know he doesn't have a black hat, since that would mean B would see 2 black hats and would immediately know the answer. So A would know their hat was white. Since A does not recognize this, it cannot be the case that your hat is black.

Rajat Raj
Jun 24, 2015

If you are wearing a white hat, then other two princes would saw that their probability of wearing a black hat is more than wearing a white hat. So they both would say black. Since both of them are wrong you must be wearing a white hat!!

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