The Schoolgirl Problem Puzzle
The Puzzle:
 | In a boarding school there are fifteen schoolgirls who always take their daily walks in groups of three. |
Give the girls letters A to O - one possible schedule is then:
The famouse Schoolgirls Problem was first posed by Reverend Thomas Kirkman in 1857. It led to a new branch of mathematics called Combinatorics.
The problem has since been described as a specific example of a Steiner Triple System. Numerous methods of solution exist, but Trial and Error still (just!) works, but you must be patient!