Notes
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The notation for numbers too big to write out Scientific notation says how big and how precise at the same time. Engineering notation gives up some of the first to line up with SI prefixes. Three nines is nearly nine hours a year 99.9 per cent sounds close to perfect. It permits eight hours and forty-six minutes of downtime, and the window it is measured over changes everything. Rounding twice gives a different answer 2.44 rounds to 2.4 then to 2, or straight to 2. Both are right, and only one of them is what you meant. Why a bread recipe adds up to more than 100 per cent Flour is 100 per cent by definition and everything else is measured against it. A 75 per cent dough totals 178 and that is correct. Board feet, tapping drills and thread pitch Four workshop numbers that are arithmetic rather than judgement, and each has one rule worth memorising. Watt-hours is the number that compares two batteries Amp-hours describe charge at some unstated voltage. Multiply by that voltage and you get energy, which is what an airline and a comparison both want. Why your photo is sideways The camera stored it landscape and attached a note saying to rotate it. Strip the note and the picture falls over. Double the radius, quadruple the area Length scales linearly, area with the square, volume with the cube. Almost every geometric surprise comes from that. Print at 100 per cent, or the squares are wrong Fit to page silently rescales everything. On graph paper, a ruler or a template, that turns a measurement into an approximation. The same emoji is not the same picture One code point, a dozen different drawings. A vendor redrawing one has changed what messages meant, more than once. A 401 means you have not said who you are Despite being named Unauthorized, it means unauthenticated. The code for "we know who you are and the answer is still no" is 403. Markdown tables are not in the standard Tables, strikethrough and task lists are all extensions. Which ones work depends entirely on what is rendering the file.
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