Benjamin Franklin believed in the importance of learning only “useful knowledge,” and he emphasized that in his various proposals for schools and academies. But that did not mean Franklin believed that learning had to be boring. Franklin found amusement in one area often considered an essential skill for budding merchants and tradesmen: mathematics.

Sometimes, though, amusement and usefulness could be at odds. After learning of a volume of “magic squares” published by Frenchman Bernard Frénicle de Bessy, Franklin reluctantly admitted that he had dabbled in the construction of these mathematical puzzles at a point when he ought to have been “employed more usefully.”

Magic squares are numerical tables in which numbers are arranged in a square in such a way that the rows, the columns, and simple diagonals all equal the same sum. The simplest form is a 3 × 3 square using numbers 1 thru 9, with each row, column, and diagonal equaling 15. No numbers are repeated. These are similar to the sudoku puzzles popular today. Here is an example of a basic magic square:

See if you can complete Franklin's Magic Square!