Poll: Does 0.99 Recurring = 1

Does 0.99 Recurring = 1

  • Yes

    Votes: 225 42.5%
  • No

    Votes: 304 57.5%

  • Total voters
    529
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Originally posted by Reezer
Another thing to think of if that since an infinite series will take forever to evaluate, the 0.99999999999r (x) will be one step further ahead of 9.9999999999r (10x). So, if you ever try to evaluate the series at any time you will end up with 9x =
9.9999999999
0.99999999999
=
8.99999999991
Yes, but there are an infinite number of nines after the decimal point, so there will be no 1. You're basically trying to say "0.9r1" and we've been over this loads of times, only with different values (with 0.9r*5=0.9r5, for example)
This falls down for the same reason that 0.9r1 is invalid (not a word, memphisto ;) ) - namely that nothing after the "0.9r" can ever exist. You can put "blue cheese" after the "r", it won't make an ounce of difference.

I'm sure most of you won't agree with that, but then I don't agree with lots that you have said.

I just don't think that it is possible to have a complete and unequestionable proof for this problem.
If you say so. All I can say is; read the proofs. Try and disprove them. Read the explanations given by us. If you find a way that has not been discussed here, by all means, feel free to post it.
If you're right, you will have contributed something great to the field of mathematics, your name will go down in history :)

Right, sod it all, I'm off to watch television. Have fun, bet this will have grown another page by the time I return.
 
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Originally posted by Deadly Ferret
Wasn't that book written by Newton? :confused:
Nope. Similar title (though the full title of Newton's tome was, apparently, Philosophiae Naturalis Principia Mathematica).
 
You know - the number of threads I've seen on this topic on various forums... it boggles the mind.

I still don't understand why this is such a difficult concept for people to grasp.

People seem to have no trouble understanding that 0.3333r = 1/3, but when it comes to understanding that 0.9999r = 1, there is massive confusion :confused:

If it isn't 1, then what is the value of (1 - 0.99999r)? It is 0.000000r = zero, and if there is no difference between the two numbers, they are identical.

I think that this 'problem' says more about how the human brain attempts to understand numbers than it does about anything relating to mathematics.
 
Originally posted by Duff-Man


If it isn't 1, then what is the value of (1 - 0.99999r)? It is 0.000000r = zero, and if there is no difference between the two numbers, they are identical.


:rolleyes:

1 - 0.9r isn't Zero, since there is zero is a constant and definite, where 1- 0.9r is a infinite number.

It's like a parabola graph, the curve will never touch Zero.
 
Originally posted by Raymond Lin

It's like a parabola graph, the curve will never touch Zero.

Do you mean hyperbola? Parabola touch zero "as standard", whereas a rectangular hyperbola hast asymptotes at the x and y axis.

/pedant.
 
Originally posted by Bodak
Do you mean hyperbola? Parabola touch zero "as standard", whereas a rectangular hyperbola hast asymptotes at the x and y axis.

/pedant.

sorry, thats what i meant, A-Level maths was so long ago. But you get my point.
 
Originally posted by VDO
...However, I am shocked. Really, utterly surprised at people's opinions. If someone wants to say that "philosophically" 0.9r!=1, they may do so, and I respect the opinions of Harley & Co. for restricting their arguments to the field of philosophy (where, unlike in Maths, there are valid opposing opinions and there can be debate), and memphisto for accepting the truth - but the people I rebutted were those claiming that, in essence, they were smarter than Stephen Hawking and every single other mathematician in history (without, of course, offering proof - perish the thought!), and people saying that, despite incontrovertible proof - even "God" himself telling them - they would refuse point blank to accept that 0.9r is mathematically equal to 1. AcidHell2 and Xenoxide, I mean you......
I think you're still missing what I'm saying. Look at your maths philosophically and ask questions, or at least, understand limits.

There are situations conventional maths systems have trouble handling. One of them, probably the biggest, is infinity and, by inference, infinitely small. Mathematicians therefore come up with a way to make those systems handle these awkward cases. Hence infinity. But infinity isn't a number. It isn't quantifiable. It's an abstract designed to stop those systems falling over when you hit the extreme case but, despite that, you're quite happy to stick an abstract like "infinity" into a system which is otherwise fully quantifiable.

And that's fine. Because it makes the system work and much of our daily lives derive (whether we realise it or not) from using those systems - like algebra.

So, all the proofs quoted (ad nauseum) work. And so they should, because the point which people have been trying to get at (that any difference betweem 0.9r and 1 is "infinitely small") is assumed out of the system used to provide those proofs, or the system wouldn't work.

Now, I have no problem with that. The system works, in the vast bulk of cases and provides us with immense benefits. But, it does nonetheless, has some incongruities. The cardinality of the sets of natural and even numbers, as I mentioned once before, is one of them.


I'm not convinced I'm getting through to the mathematicians here what I'm getting at, about challenging your systems. Maybe I'm just not wording it very well. I may be wrong, and apologise if I am , but I distinctly get the impression that the "philosophical" line of argument is being dismissed (as in VDO's quote above), perhaps as some sort of fluffy, artsy, non-scientific stuff not worthy of the attention of a scientist or mathematician. If I'm right in that, then wake up. Questioning your assumptions, and even the foundations of maths, leads to a greater understanding, not a lesser one. Otherwise, all you're doing with even advanced maths is mechanistically applying the system. It might be a complex system to understand, but it would still make you a mechanic. Don't be put off by the word "philosophical". Philosophy in general might relate to a nebulous understanding "the meaning of life, the universe and everything" (\Hitchhikers Guide mode off) but the philosophy of mathematics is about using reason to understand the theories and ideas of maths, to question the limits and principles in order to further that knowledge.


Anyway, if so, I found a document that just might make you reassess that judgement. I only found it this morning, so I haven't been using it as a crib sheet for my comments. You will, however, have to take my word for it. In fact, I haven't finished reading it myself yet, but the line of argument it takes will, hopefully, make you realise what I've been getting at all this time. To add some weight, it is an article written by a member of the Mathematics Education Research Centre at Warwick University, so this is not just the opinion of some bloke on a forum, it's the work of a maths academic.

Once again, though, I've never said your proofs don't work. My point is that there's more than one way of looking at it. I'm not trying to undermine your methodology, or to dismiss the results. I'm trying to make you think more about what assumptions you make when you use these methods, and to adopt what I can only ascribe as being a more enlightened and less dogmatic view. That's what I've meant (and maybe some others here have too) about another viewpoint, or 'thinking outside the box'.

The document is here

Please, Alpha, VDO, xyphic, etc - take a look.
 
Please let's not associate "philosophy" with believing that 0.9r != 1 and mathematics with 0.9r = 1. The link you posted, is someone's opinion albeit a professional mathematician/philosopher, but that doesn't make them right; there are plently of philosophers who would disagree with it.

Harley, I'm afraid in this case you might just be wrong and have misunderstood the subtle reasoning that it takes to see that 0.9r actually refers to the same concept as "1".
 
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OK, so generally speaking all the vaguely intelligent people have established that 0.9r = 1.;)

SO, what is the largest number less than 1?

Thinks about it, and there is no answer!!
 
Very interesting link that Harley, cheers for posting it :)

Am muddling my way through it, don't have any Maths training beyond A-level, but the ol' scientific mind is kicking in and I think it's making sense :p

*edit* Hehe 45 pages, maybe something for after work :p
 
I absolutely cannot believe this is still going.

Philosophically, is 4=5? I can tell you mathematically it isn't, but hey, with philsophy, you can prove anything! I must be right because I just said so!!

Oh, and for the "it tends to 1, but doesn't equal it" crowd, integrals all tend towards their answer, and yet maths treats it as equal.
 
0.9 recurring is 1

The 200 odd who voted against are wrong.

Unless of course they keep falling back on arguments based on the fact that nothing can be "proved" - yes Maths is based on concepts we can't define - we just think we know what they mean and everyone understands. So please do utilise these arguments, but next time you check your bank statement and your life savings are gone accept that the bank can use the same arguments to spindle you out of the money.

I cannot believe this has caused 30 pages of debate.
 
Originally posted by growse
I absolutely cannot believe this is still going.

Philosophically, is 4=5? I can tell you mathematically it isn't, but hey, with philsophy, you can prove anything! I must be right because I just said so!!

Oh, and for the "it tends to 1, but doesn't equal it" crowd, integrals all tend towards their answer, and yet maths treats it as equal.

I think you misunderstand philosophy.

It can't be used to prove anything=anything, thats not how it works. Philosophy is based on solid logic, and logical arguments. In fact, the first philosopher was Pythagoras, at least he coined the phrase, and many philosophers thorugh history were incredibly competant mathematicians in their own right.

A standard example of a philosophical argument would run something like :

1. All men are mortal - Assumption
2. I am a man - Statement
3. I am mortal - Conclusion

In this case, as long as the initial assumption is true, then the argument, because it is logical, must stand, and the conclusion must be true.

You'll notice that mathematical proof works in exactly the same way. Assumptions are made, and a logical progression is made towards a conclusion, that is subsequently unchallengable, provided that the initial assumptions hold.

I'm not making any comment about where I stand, one way or another, just trying to explain that philosophy is not an airy-fairy subject where you can just say any old thing, and it can never be proved or disproved.
 
Originally posted by Raymond Lin
where 1- 0.9r is a infinite number.
How's it an infinite number? You accept that 0< 0.9r < 2 right? Then that implies -1 < 1-.9r < 1.
Last time I checked, 1 and -1 weren't infinite were they?
Originally posted by Reezer
I did study maths, I did maths and further maths at A level and got two A's...
Then you must be familiar with the Gaussian sum for infinite series then? Do you deny that its true?
Originally posted by Reezer
Another thing to think of if that since an infinite series will take forever to evaluate, the 0.99999999999r (x) will be one step further ahead of 9.9999999999r (10x). So, if you ever try to evaluate the series at any time you will end up with 9x =
9.9999999999
0.99999999999
=
8.99999999991

Which is not 9 as the proof requires...
Shame you didn't understand the concept of infinity then, because thats incorrect, how can you have a "last place" in an infinitely long series? Every time you say "Here's the last one, thats where the "one step" is" I'll just say "Nope, there's another 9 after that". So where's the "one step"?
Originally posted by Reezer
I just don't think that it is possible to have a complete and unequestionable proof for this problem.
You must have got your A's by "parrot fashion", not be understanding the nature of the things you learnt.
 
Originally posted by Phog
Why dont people just accept that 0.99r = 1
Because they try to relate things that don't exist to things that do exist, and doing so introduces problems in their understanding, since such a linking is not possible. Then when they can't relate it to real things, they claim its "physically impossible" when physics has nothign to do with it.

If your logic leads you to the result 1 is bigger than infinity, you'd normally realise you're in error, but it seems some people don't.
 
x = 0.9r
10*x=9.9r
10*x - x=9.9r - 0.9r
9x = 9
x=1

This proof has been stated a few times, and I like it, its logical, and doesn't leave any room for interpretation.

Question for the maths people though ( and this isn't a loaded question, I'm just looking for information )

Since multiplication and division, which are both used in the proof, can't be proved as consistent ( Godel's Incompleteness Theory ) is there really no room for error here?

Now, I'd be the first to admit there's no way I'm going to read or understand the theory itself, I was under the impression that since multiplication and division are part of the axioms of mathematics, and can't be proved, then the above sum could be wrong, or at least can't be proved to be correct.
 
Originally posted by AlphaNumeric
How's it an infinite number? You accept that 0< 0.9r < 2 right? Then that implies -1 < 1-.9r < 1.
Last time I checked, 1 and -1 weren't infinite were they?

Perhaps i shoul dhave put it clearer, the r in 0.9r means the 9999 is infinite. thats what i meant, however how close the 0.9999999999999999999999999999 gets to 1, it will never be 1.

So how can 0.9r = 1?

If 0.9r does = 1, then why do we even have the "number" 0.9r ?

I don't claim to be clever or oxbridge educated, but i just don't see it.

Does Pi = 3.14? or do you accept it's Pi ?
 
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