the.com/rounding
the polite lie numbers tell so humans can think about them.
means replacing a precise number with a simpler nearby one at a chosen level of accuracy, trading truth for usability.
from from middle english round, from old french roont, from latin rotundus meaning wheel-shaped; the numerical sense arrived once merchants realized nobody needs the ninth decimal to sell grain.
banker's roundingrounds ties to the nearest even digit, not always up
floating pointcomputers round constantly, causing 0.1+0.2 to misbehave
election mathrounding percentages can make vote shares sum past 100
pi in schoolsoften rounded to 3.14, engineers use far more digits
for instance
eu seat allocation — parliament seats rounded via divisor methods, sparking disputes since the 1980s
y2k bug — dates truncated to two digits, a rounding cousin that cost billions
nasa mars climate orbiter — unit and precision errors in 1999 crashed a $327m probe
grade curves — 89.4 percent rounds to an a minus in most us schools