The honest prince

This Riddler puzzle is about randomly generating convex quadrilaterals.

You’re the most eligible bachelorette in the kingdom, and you’ve decided to marry a prince. The king has invited you to his castle so that you may choose from among his three sons. The eldest prince is honest and always tells the truth. The youngest prince is dishonest and always lies. The middle prince is mischievous and tells the truth sometimes and lies the rest of the time. Because you will be forever married to one of the princes, you want to marry the eldest (truth-teller) or the youngest (liar) because at least you know where you stand with each. But there’s a problem: You can’t tell the princes apart just by looking, and the king will grant you only one yes-or-no question that you may address to only one of the brothers.

What yes-or-no question can you ask that will ensure that you do not marry the middle prince?

Here is my solution:
[Show Solution]

One thought on “The honest prince”

  1. Nice solution! Another solution is to ask “Would you say ‘yes’ if I asked you if this prince (pointing to B) is the middle prince?”. If the answer is “No”, choose prince B; otherwise, choose prince C. My solution is pretty similar to the “heaven and hell” riddle. I think your solution is easier to understand, just thought I would share another approach.

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