Here’s a simple number game to play on a rainy day, or while sheltering in place. You and I take turns crossing out numbers from the list {1, 2, 3, …, 9}. The winner is the last person to cross out a ...

Some of the most satisfying number puzzles require little mathematical know-how. In fact, cracking the one below calls for thinking that is quite nonmathematical. I don’t know where or when I first ...