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# Proving 0.999... Is Equal to 1

#### eldavojohn (898314) writes | more than 3 years ago

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eldavojohn (898314) writes "Some of the juiciest parts of mathematics are the really simple statements that cause one to immediately pause and exclaim "that can't be right!" But a recent 28 page paper in The Montana Mathematics Enthusiast (PDF) spends a great deal of time fielding questions by researchers who have explored this in depth and this seemingly impossibility is further explored in a brief history by Dev Gualtieri who presents the digit manipulation proof: Let a = 0.999... then we can multiply both sides by ten yielding 10a = 9.999... then subtracting a (which is 0.999...) from both sides we get 10a — a = 9.999... — 0.999... which reduces to 9a = 9 and thus a = 1. Mathematicians as far back as Euler have used various means to prove 0.999... = 1."

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