# Three knights or knaves, three different hair colors

In a group of three people (A, B and C), everyone has a different hair color (blond, black or brown, not necessarily in this order) and everyone may be either a knight (always telling the truth) or a knave (always lying). This is what they say.

• Blond-haired person: "C has brown hair".
• Black-haired person: "C is a knave".
• Brown-haired person: "A and B are knights".

Determine the hair color of C.

• A tiny little doubt - According to your question, is it that they all are knights or all are knaves. or one knight and the others knaves and so on. May 19, 2019 at 11:55
• @Ak19 Each of them can be either a knight or a knave - they don't have to be all of the same kind. May 19, 2019 at 11:56
• @Ak19 - In fact, they cannot all be the same kind by the second question. If they're all knaves or all knights, the black-haired person could not say that "C is a knave". May 19, 2019 at 16:10

One possibility is that

The brown-haired person and black-haired person are A and B in some order. Then since they are both knights, the black-haired person speaks the truth when he says that C is a knave.

This means that

C is the blond-haired man, who is clearly lying when he says that C has brown hair (because he's describing himself!) Therefore C has blond hair.

• oops sniped... bye May 19, 2019 at 12:22
• coming back with explanations for other cases :) +1! May 19, 2019 at 12:28
• I'll accept your answer because you were the first to answer correctly, but how did you rule out all the other cases? May 19, 2019 at 13:01

Blond

Explanation

See the following images... they also explain the other cases

Conclusion

C is a knave with blond hair, A and B are knights with black/ brown hair

El- Guest and OK have got the answer before me..

C is

Blond haired

Explanation

First let's start from the black haired person. If he were a knight, C would be a knave and can't have black hair. If he were a knave it would directly imply that C can't have black hair. (as he would be telling about himself in both cases)  Next from the blond haired person. If he were a knight, then C would have brown hair. Now C can be a knight or a knave. If C were a knight, A and B both would be knights with any one of them with black hair. So, this would imply that C is a knave. But this is a contradiction. So if C were a brown-haired knave, A and B would be knaves with any one blond-haired. This would imply that blond haired person is a knave, again a contradiction.  So, the blond haired person must be a knave and it must be C .