Poll: Does 0.999.. equal 1 ?

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JackEmpty

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Apr 6, 2011
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I paraphrase my post above:

This is not an open question.

.(9) = 1 is a theorem.

If you say it is incorrect you are wrong.
 

Thaliur

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Jan 3, 2008
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Apparently, at this point the poll was answered by 118 people with a mathematical mind and 101 with an engineering-compatible (AKA pragmatic or realistic) mind.
 

maninahat

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I originally picked no, despite seeing all the various proofs to the contrary (which are infact correct). I, like a lot of people, was incapable of understanding how 0.999... = 1

Human perception makes it hard to accept the idea. We think to ourselves, "but the 9s go on forever! They will always get closer to 1, but never reach it." Unfortunately, the nature of infinity and infinity small numbers works in a highly counter-intuitive fashion: it is entirely because the 9s go on forever that you can't say it is any less than 1.

The straight dope article gives a practicle example of this problem, known as Zeno's paradox: If a man is racing against a tortoise, and the tortoise has a ten meter head start, you would expect the man to reach the tortoise very quickly. But by the time the man has run the ten metres, the tortoise has moved foward 1 meter. By the time the man has run another meter, the tortoise will have gone on another .10 meter, and so on and so forth. If this goes on for infinity, how can the man ever overtake the tortoise?

In the real world, we know that the man can obviously overtake the tortoise in barely any time, so what does this say about the nature of infinity? Just because it goes on forever, doesn't make it an unachievable task.
 

Zantos

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Most analytical proofs rely on the fact that you can make small perturbations to an object without it altering it (these are usually denoted epsilon or delta). So by the same logic any infinitessimal difference between 0.999... and 1 is mathematically insignificant. Although if you study analysis you should already know decimals are a really bad way of trying to express irrational numbers anyway.
 

Dave Davey

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Apr 8, 2011
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0.999... = 1.000...

This is universally agreed upon by mathematicians and scientists - basically, people who are experts in the nitty gritty of mathematics.

As everyone else has said, Wikipedia is your go-to place for proofs of this fact.

Common arguments against it are things like 'Oh, but there's an infinitesimally small amount between them' - NO THERE'S NOT, that's the whole point.

Whether you like it or not, mathematics allows us to prove things that our little fleshy brains might not like. Did you know you can draw a shape with finite area and infinite perimeter?

Infinity is not for the faint of heart. 0.999... is as equal to 1 as 4/8 is equal to a half. They are numerically identical, two difference ways of writing the same scalar value.
 

Volkov

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Dec 4, 2010
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Thaliur said:
Apparently, at this point the poll was answered by 118 people with a mathematical mind and 101 with an engineering-compatible (AKA pragmatic or realistic) mind.
Incorrect. Vast majority of engineers know math past 5th grade, and so will correctly answer that the two numbers are equal. Again, this is not an opinion, an open discussion, or a debate.

"Pragmatic/realistic" mind will also realize, that a *number* and a *usable in practice* number are two different things, and in this question *usable in practice* was never raised. Therefore, *numbers* are being considered.
 

Volkov

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Also, there is no such thing as "equivalent" in mathematical terms. The two numbers are EQUAL, not equivalent.
 
Feb 13, 2008
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maninahat said:
The straight dope article gives a practicle example of this problem, known as Zeno's paradox: If a man is racing against a tortoise, and the tortoise has a ten meter head start, you would expect the man to reach the tortoise very quickly. But by the time the man has run the ten metres, the tortoise has moved foward 1 meter. By the time the man has run another meter, the tortoise will have gone on another .10 meter, and so on and so forth. If this goes on for infinity, how can the man ever overtake the tortoise?
Zeno's paradox confuses by talking about distance, but measuring with time. Given the Paradox as it stands, the Man can never pass the tortoise because the time at which he does is never reached.

This is why the equivalency was brought in, but also why 0.9 recurring cannot equal 1. Because .9 recurring cannot finitely exist; it is, in itself, an irrational number - therefore it has a rational equivalency of 1. It can't equal 1, because 1 is rational.

If people want to argue and throw wiki's at me, then that's fair enough. But I'd also challenge you to find a definition of a solid material that's over 99% space - which is what it's like in real physics (Atomic Theory).

Volkov said:
Also, there is no such thing as "equivalent" in mathematical terms. The two numbers are EQUAL, not equivalent.
http://en.wikipedia.org/wiki/Equivalence_relation

*rolls eyes*
 

Volkov

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ravensheart18 said:
Equal, and so close we can treat them equal, are not the same.

Equal, and different but base 10 has trouble displaying the difference is not the same.

.9999 is not = 1.
So what's the difference between the two? Express it in any way you like, doesn't have to be base 10.
 

rokkolpo

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Wolfenbarg said:
ZiggyE said:
No it doesn't. The gap is so infinitesimal that it hardly counts, but 0.9999 recurring does not equal one.
Untrue. It goes 0.999... on to infinity. You'd think logically, you would just add a number that went 0.000...1. However, you can't have a 1 at the end of an infinite number of zeros, for that assumes there is an end to infinity, which there isn't. In mathematics, everything needs to be proven, and all the proofs say that 0.999... = 1. Whether you use rounding, limits, or just absolute practical value, they are identical.

Also, you have to remember that such a number would be identical to a level so infinitely small that no physical measurement could possibly amount to it. The decimal limits go down to a point that is smaller than any subatomic particle, and therefore, non-existent for any argument.
I like this explanation.^^

It seems to make sense, though I wouldn't know.
 

Volkov

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The_root_of_all_evil said:
maninahat said:
The straight dope article gives a practicle example of this problem, known as Zeno's paradox: If a man is racing against a tortoise, and the tortoise has a ten meter head start, you would expect the man to reach the tortoise very quickly. But by the time the man has run the ten metres, the tortoise has moved foward 1 meter. By the time the man has run another meter, the tortoise will have gone on another .10 meter, and so on and so forth. If this goes on for infinity, how can the man ever overtake the tortoise?
Zeno's paradox confuses by talking about distance, but measuring with time. Given the Paradox as it stands, the Man can never pass the tortoise because the time at which he does is never reached.

This is why the equivalency was brought in, but also why 0.9 recurring cannot equal 1. Because .9 recurring cannot finitely exist; it is, in itself, an irrational number - therefore it has a rational equivalency of 1. It can't equal 1, because 1 is rational.

If people want to argue and throw wiki's at me, then that's fair enough. But I'd also challenge you to find a definition of a solid material that's over 99% space - which is what it's like in real physics (Atomic Theory).
These are several incorrect statements.

1. 0.(9) can finitely exist. It exists as 1.0.
2. It is NOT an irrational number.
3. There is no such thing as "rational equivalency" of an irrational number.

This is not an argument. This is a precise mathematical statement based on direct, unambiguous conclusions from founding axioms of real number arithmetic, versus numerous incorrect statements using incorrect terms. Only one side is correct.

Solid matter is matter which can sustain shear, tensile stress, and therefore can hold shape without boundary forces acting on it. It has nothing to do with atom density, mass density, or anything similar. Therefore asking for "a definition of solid material that's over 99% space" is like "asking for definition of the term 'video game' that necessarily mentions erythrocytes." The two are entirely unrelated, and therefore the latter will not be in the definition of the former.
 

tjarne

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Oct 15, 2009
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I would say it's a good enough approximation for practical purposes. What else is needed? Just as small angles are treated as 1
 

Volkov

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The_root_of_all_evil said:
Volkov said:
Also, there is no such thing as "equivalent" in mathematical terms. The two numbers are EQUAL, not equivalent.
http://en.wikipedia.org/wiki/Equivalence_relation

*rolls eyes*
I forgot about this, my bad. You are right, equivalence relations are defined. Equality of two numbers is one of them.