how never to lose a game: the order of moves, answers to the first move and the two-corner trap
Built as a memo rather than a table: the thing worth hanging it up for reads across the room, with the full reference in smaller type below it.
Three sizes in one archive — from a sheet on the fridge to a poster on the wall.
Two players take turns placing their mark in a free cell of a 3 × 3 board; the cross goes first. Three in a line wins; a full board with no line is a draw.
Two players take turns picking numbers from 1 to 9, each once; whoever first holds three that add up to 15 wins. In the square 2 7 6 · 9 5 1 · 4 3 8 every row, column and diagonal adds up to 15, and no other three do: exactly 8 triples, one per line of the board. So it is the same game.
Why the numbers can be trusted. Every countable number here is computed from data rather than typed in, and the sheet must pass 4 independent checks before it is allowed to build — how many items there are, the order they come in, and the claim in the highlighted box itself. If one fails, there is no file.
the IWF colour code and the plate count: from target weight to each side of the bar, no calculator
why a “yes” from a test that is right 99 times in 100 is wrong more than nine times in ten when one in a thousand has the thing
the first digit of a number: why a one turns up more than six times as often as a nine, and in which sets that is true
how many people it takes for two of them to share a birthday — and the same count for codes and fingerprints