Can somebody explain this to me?

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Discussion Overview

The discussion revolves around the mathematical concept of the decimal representation of numbers, specifically addressing the relationship between the repeating decimal 0.999... and the number 1. Participants explore the implications of this relationship and the definitions involved in decimal representation.

Discussion Character

  • Exploratory, Technical explanation, Debate/contested

Main Points Raised

  • One participant references a video and seeks an explanation of a mathematical trick related to decimal representation.
  • Another participant suggests searching for existing threads on the equivalence of 0.99... and 1, indicating that this is a common topic of discussion.
  • One participant argues that there is a distinction between real numbers and their numeral representations, using the example of 1/2 and 2/4 to illustrate that different decimal representations can refer to the same real number.
  • This participant proposes a definition of real numbers represented by infinite decimals as the smallest number not smaller than any finite decimal approximations, concluding that the smallest number not smaller than the sequence .9, .99, .999, ... is 1.00000.
  • Another participant defines the decimal representation 0.a1a2a3... as the limit of a sequence of finite decimal approximations, specifically stating that the limit of the sequence 0.9, 0.99, 0.999, 0.9999, ... is 1, using a geometric series to support this claim.

Areas of Agreement / Disagreement

Participants express differing views on the interpretation of decimal representations and their implications, indicating that multiple competing views remain without a consensus on the matter.

Contextual Notes

Some participants rely on specific definitions of real numbers and limits, which may not be universally accepted. The discussion includes assumptions about the nature of decimal representation and the convergence of sequences.

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There are lots of threads on here discussing "0.99...=1." Try searching!
 
the point is there is a difference bewteen a real number and the numerals used to represent it.

just as 1/2 = 2/4, there are more decimals than there are reals, and1.000, and .99999 represent the same real.

one way to see this is to define the real number represented by an infinite decimal as the smallest number not smaller than any of the finite decimal approximations. then one eventually sees that the smallest number not smaller than.9, .99, .999, ... is 1.00000.

if one does not eventually see this, one continues to post it here ad infinitum.
 
The definition of the decimal representation 0.a1a2a3... is the limit of the sequence 0.a1, 0.a1a2, 0.a1a2a3, ...
In particular, 0.999... means the limit of the sequence 0.9, 0.99, 0.999, 0.9999, ... Since that is a geometric sequence, it is easy to show that its limit is [itex]\frac{0.1}{1- .9}= 1.[/itex]
 

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