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'Weekly Problem 35 - 2010' printed from http://nrich.maths.org/
The first person cannot be telling the truth since if all the
others are knaves, this contradicts that they are telling the truth
when they say the person in front is a knave.
The second person says the first is a knave so is telling the
truth; he is a knight.
The third says this knight is a knaveso he is lying; he is a knave.
Continuing in this way we see that there is an alternating sequence
of 13 knaves and 12 knights.
This problem is taken from the UKMT Mathematical Challenges.View the previous week's solutionView the current weekly problem