Why does an infinite number of .3's not equal 1/3?

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  • Thread starter Thread starter Algr
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Discussion Overview

The discussion revolves around the question of why an infinite series of 0.3's does not equal 1/3. Participants explore concepts related to infinite decimals, limits, and the nature of real numbers, touching on both theoretical and mathematical reasoning.

Discussion Character

  • Debate/contested
  • Mathematical reasoning
  • Conceptual clarification

Main Points Raised

  • Some participants argue that an infinite number of positive values should equal infinity, questioning how an infinite series of 0.3's can equal 1/3.
  • Others propose that the sequence of partial sums of the series can be defined mathematically, leading to the conclusion that 0.333... equals 1/3.
  • A participant suggests that the concept of limits is essential in understanding how 0.333... can be represented as a fraction, while another questions the validity of this approach, suggesting it relies on circular logic.
  • Some participants clarify that the process of adding an infinite number of 3's does not yield 1/3, and that limits must be invoked to understand the convergence of the series.
  • There are discussions about the implications of multiplying by infinity and the undefined nature of certain operations involving infinity, with some participants asserting that infinity is not a real number.
  • One participant raises concerns about the assumptions underlying calculus and limits, suggesting that they may not adequately justify the equality of 0.333... and 1/3.

Areas of Agreement / Disagreement

Participants express a range of views, with no consensus reached on the nature of infinity, the validity of limits, or the equality of 0.333... and 1/3. The discussion remains unresolved, with competing interpretations and arguments presented.

Contextual Notes

Limitations include differing definitions of infinity, the role of limits in calculus, and the assumptions made in mathematical reasoning regarding infinite series. The discussion highlights the complexity of these concepts without resolving them.

  • #61
zgozvrm said:
This discussion is beyond converting fractions to decimals and vice-versa, so if that is beyond your level of math, then so is this discussion.

Maybe you could prove to us all why the division algorithm necessarily works?

Why it cannot produce garbage as long as the divisor is non-zero?
 
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  • #62
zgozvrm said:
You guys are all over-thinking this. Algr didn't seem to believe something was true, I showed him a way to see that it WAS in fact true, therefore, I proved it to him.[/b]

I think you are UNDER-thinking things, Zgozvrm. You can't assume that a proof is correct simply because it gives you the answer you want. That is circular logic.

Edit:
In your latest proof, I don't have a problem with step 1, but in step 2, there is no final result of the division. You simply DECLARE the result to be ".333..." as one would declare a variable. That doesn't prove anything about what it means for a decimal to repeat infinitely.
 
Last edited:
  • #63
I think you are UNDER-thinking things, Zgozvrm. You can't assume that a proof is correct simply because it gives you the answer you want. That is circular logic
Indeed, Algr!

"Plug&chug"-mentalities confuse their ability to churn something out of a machine with what is required as proof.
 
  • #64
Algr said:
Edit:
In your latest proof, I don't have a problem with step 1, but in step 2, there is no final result of the division. The "..." simply represents a failure to complete a process that can never be completed.

Why is representability (or lack of such) obvious?

I just stopped at the first hurdle, so I haven't reached the other three yet. :smile:
 
  • #65
Wow! Apparently you guys don't believe the basic laws of math nor that division is a valid "algorithm" with non-zero numbers.

I shouldn't have to re-invent the wheel to make a point. If I told you that 2+5=7, we all know this is true, and I shouldn't have to prove it to anyone in a discussion that is beyond that level of math.

The assumption was made all along that people know how to divide and "convert" a fraction to a decimal.

I cannot help either of you if you are not willing to accept or understand the basic laws of math, nor am I willing to try. That is way beyond the scope of this discussion.


Any further posts along these lines will not be answered and/or acknowledged by me.
 
  • #66
zgozvrm said:
Wow! Apparently you guys don't believe the basic laws of math nor that division is a valid "algorithm" with non-zero numbers.
No, we don't.

Rather, we strive to construct consistent, mathematical systems, rather than rely upon "received wisdom" as some sort of oracle.
 

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