This is a simple puzzle, hopefully the younger ones will like it too. I got inspired by this puzzle through Alok Mittal’s last Mathematical Circles class on “truth tellers and liars”. This puzzle is taken from Martin Gardner’s “The Colossal Book of Short Puzzles and Problems“, Chapter 13 which has many puzzles on truths and lies. This is an adaptation from an original puzzle by Martin Hollis in Tantalizers.
A boy and a girl are sitting on the front steps of their building.
“I am a boy,” said the one with black hair.
“I am a girl,” said the one with red hair.
If at least one of them is lying, who is which?
As always, please send your answers directly to me at firstname.lastname@example.org. If you like the puzzle, please share it with others. If you have interesting puzzles to share, please send them to me at my e-mail given above.