Logic. It’s a logical place to start: logical deduction is the ground rule of all mathematical puzzles. Indeed, logic is the foundation of all mathematics. In the nomenclature of puzzledom, however, ‘logic problems’ are brainteasers that employ deductive reasoning alone – shunning, for example, any type of arithmetical calculation, algebraic manipulation, or sketching of shapes on the backs of envelopes. They are the most accessible type of mathematical conundrum because they require no technical knowledge, and the questions easily lend themselves to humorous phrasing. But, as we shall see, they are not always the easiest to solve, since they twist our brains in unfamiliar ways.
Which they have been doing since at least the time of Charlemagne, King of the Franks.
In 799 CE, Charlemagne, who ruled over much of Western Europe, received a letter from his old teacher, Alcuin: ‘I have sent you’, it read, ‘some arithmetical curiosities to amuse you.’
Alcuin was the greatest scholar of his era. He grew up in York, attending and then running the city’s cathedral school, the best educational establishment in the coun
