Practice & Puzzles

Reading about a method and using one are different activities, and only the second produces anything durable. These articles are the practice side of the site: problems with the setup, the working, and the reasoning laid out, so you can attempt them first and check afterwards.

The puzzles here are chosen because they’re enjoyable as well as instructive. Age problems, digit sums, coins, and consecutive-number puzzles have survived for centuries because they hide real algebraic structure behind a friendly surface.