It was well known amongst his colleagues that professor Ambrose Helleborus would leave the house and later return without his hat, as a matter of fact, according to his housekeeper, Mrs. MacGillicuddy, this would regularly occur once after every four excursions on the town.
On a windy winter’s day, professor Ambrose Helleborus went to the university library to do some research on the legendary Kingdom of Agartha, after which he went to enjoy a tasty lunch at the Chez Antoine café, whereafter he spent a leisurely afternoon with cronies at the Jolly Hills Chess Club.
Subsequently, professor Ambrose Helleborus returned home without his hat, facing extensive interrogation by Mrs. MacGillicuddy, who would have to retrace his steps and retrieve the hat, as it was a treasured gift from professor Einstein.
But Mrs. MacGillicuddy didn’t mind as she by now had developed a circle of chat friends along professor Ambrose Helleborus’ usual excursion routes.
What are the respective probabilities that professor Ambrose Helleborus left his hat at the university library, Chez Antoine’s and the Jolly Hills Chess Club?