how to subtract from 10, 100, 1000… with no borrowing, digit by digit
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.
A round number here is a 1 followed by zeros: 10, 100, 1000… The number taken away is a positive whole number smaller than it.
Blaise Pascal began work on his calculator in 1642, while assisting his father, the supervisor of taxes in Rouen. Its wheels turned only one way, so it could only add, and subtraction was done with nines’ complements. Above each result digit stood a second one, its complement (to 9 on the decimal wheels), and a bar covered one row or the other.
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