That’s the best explanation of this I’ve ever seen, thank you!
Comment on I just cited myself.
Karcinogen@discuss.tchncs.de 4 months ago2/9 = 0.222… 7/9 = 0.777…
0.222… + 0.777… = 0.999… 2/9 + 7/9 = 1
0.999… = 1
No, it equals 1.
Crozekiel@lemmy.zip 4 months ago
zarkanian@sh.itjust.works 4 months ago
That’s more convoluted than the 1/3, 2/3, 3/3 thing.
3/3 = 0.99999… 3/3 = 1
If somebody still wants to argue after that, don’t bother.
Dagrothus@reddthat.com 4 months ago
Nah that explanation is basiclaly using an assumption to prove itself. You need to first prove that 1/3 does in fact equal .3333… which can be done using the ‘convoluted’ but not so convoluted proof
skulblaka@sh.itjust.works 4 months ago
Sure, when you start decoupling the numbers from their actual values. The only thing this proves is that the fraction-to-decimal conversion is inaccurate. Your floating points (and for that matter, our mathematical model) don’t have enough precision to appropriately model what the value of 7/9 actually is. The variation is negligible though, and that’s the core of this, is the variation off what it actually is is so small as to be insignificant and, really undefinable to us - but that doesn’t actually matter in practice, so we just ignore it or convert it. But at the end of the day 0.999… does not equal 1. A number which is not 1 is not equal to 1. That would be absurd. We’re just bad at converting fractions in our current mathematical understanding.
myslsl@lemmy.world 4 months ago
You are just wrong.
The rigorous explanation for why 0.999…=1 is that 0.999… represents a geometric series of the form 9/10+9/10^2+… by definition, i.e. this is what that notation literally means. The sum of this series follows by taking the limit of the corresponding partial sums of this series (see here) which happens to evaluate to 1 in the particular case of 0.999… this step is by definition of a convergent infinite series.
barsoap@lemm.ee 4 months ago
The only thing this proves is that the fraction-to-decimal conversion is inaccurate.
No number is getting converted, it’s the same number in both cases but written in a different representation. 4 is also the same number as IV, no conversion going on it’s still the natural number elsewhere written
S(S(S(S(Z)))). Also decimal representation isn’t inaccurate, it just happens to have multiple valid representations of the same number.A number which is not 1 is not equal to 1.
Good then that 0.999… and 1 are not numbers, but representations.
bitfucker@programming.dev 4 months ago
Lol I fucking love that successor of zero
IntriguedIceberg@lemmy.world 4 months ago
It still equals 1, you can prove it without using fractions: x = 0.999… 10x = 9.999… 10x = 9 + 0.999… 10x = 9 + x 9x = 9 x = 1
There’s even a Wikipedia page on the subject
Clinicallydepressedpoochie@lemmy.world 4 months ago
I hate this because you have to subtract .99999… from 10. Which is just the same as saying 10 - .99999… = 9
Which is the whole controversy but you made it complexicated.
Laser@feddit.org 4 months ago
You don’t subtract from 10, but from 10x0.999… I mean your statement is also true but it just proves the point further.
ColeSloth@discuss.tchncs.de 4 months ago
Do that same math, but use .5555… instead of .9999…
BeardedGingerWonder@feddit.uk 4 months ago
Have you tried it? You get 0.555… which kinda proves the point does it not?
Wandering_Uncertainty@lemmy.world 4 months ago
???
Not sure what you’re aiming for. It proves that the setup works, I suppose.
x = 0.555…
10x = 5.555…
10x = 5 + 0.555…
10x = 5+x
9x = 5
x = 5/9
5/9 = 0.555…
So it shows that this approach will indeed provide a result for x that matches what x is supposed to be.
Hopefully it helped?
tuna@discuss.tchncs.de 4 months ago
If they aren’t equal, there should be a number in between that separates them. Between 0.1 and 0.2 i can come up with 0.15. Between 0.1 and 0.15 is 0.125. You can keep going, but if the numbers are equal, there is nothing in between.
What number comes between 0.999… and 1?
IsoSpandy@lemm.ee 4 months ago
My brother. You are scared of infinities. Look up the infinite hotel problem. I will lay it out for you if you are interested.
Image you are incharge of a hotel and it has infinite rooms. Currently your hotel is at full capacity… Meaning all rooms are occupied. A new guest arrives. What do you do? Surely your hotel is full and you can’t take him in… Right? WRONG!!! You tell the resident of room 1 to move to room 2, you tell the resident of room 2 to move to room 3 and so on… You tell the resident of room n to move to room n+1. Now you have room 1 empty
But sir… How did I create an extra room? You didn’t. The question is the same as asking yourself that is there a number for which n+1 doesn’t exist. The answer is no… I can always add 1.
Infinity doesn’t behave like other numbers since it isn’t technically a number.
So when you write 0.99999… You are playing with things that aren’t normal. Maths has come with fuckall ways to deal with stuff like this.
Well you may say, this is absurd… There is nothing in reality that behaves this way. Well yes and no. You know how the building blocks of our universe obey quantum mechanics? The equations contain lots of infinities but only at intermediate steps. You have to “renormalise” them to make them go away. Nature apparently has infinities but likes to hide the from us.
The infinity problem is so fucked up. You know the reason physics people are unable to quantize gravity? Surely they can do the same thing to gravity as they did to say electromagnetic force? NOPE. Gravitation doesn’t normalise. You get left with infinities in your final answer.
Anyways. Keep on learning, the world has a lot of information and it’s amazing. And the only thing that makes us human is the ability to learn and grow from it. I wish you all the very best.
barsoap@lemm.ee 4 months ago
But sir… How did I create an extra room? You didn’t.
When Hilbert runs the hotel, sure, ok. Once he sells the whole thing to an ultrafinitist however you suddenly notice that there’s a factory there and all the rooms are on rails and infinity means “we have a method to construct arbitrarily more rooms”, but they don’t exist before a guest arrives to occupy them.
frezik@midwest.social 4 months ago
It’s a correct proof.
One way to think about this is that we represent numbers in different ways. For example, 1 can be 1.0, or a single hash mark, or a dot, or 1/1, or 10/10. All of them point to some platonic ideal world version of the concept of the number 1.
What we have here is two different representations of the same number that are in a similar representation. 1 and 0.999… both point to the same concept.
Tlaloc_Temporal@lemmy.ca 4 months ago
I strongly agree with you, and while the people replying aren’t wrong, they’re arguing for something that I don’t think you said.
1/3 ≈ 0.333… in the same way that approximating a circle with polygons of increasing side number has a limit of a circle, but will never yeild a circle with just geometry.
0.999… ≈ 1 in the same way that shuffling infinite people around an infinite hotel leaves infinite free rooms, but if you try to do the paperwork, no one will ever get anywhere.
Decimals require you to check the end of the number to see if you can round up, but there never will be an end. Thus we need higher mathematics to avoid the halting problem. People get taught how decimals work, find this bug, and then instead of being told how decimals are broken, get told how they’re wrong for using the tools they’ve been taught.
If we just accept that decimals fail with infinite steps, the transition to new tools would be so much easier, and reflect the same transition into new tools in other sciences. Like Bohr’s Atom, Newton’s Gravity, Linnaean Taxonomy, or Comte’s Positivism.
barsoap@lemm.ee 4 months ago
Decimals require you to check the end of the number to see if you can round up, but there never will be an end.
The character sequence “0.999…” is finite and you know you can round up because you’ve got those three dots at the end. I agree that decimals are a shit representation to formalise rational numbers in but it’s not like using them causes infinite loops. Unless you insist on writing them, that is. You can compute with infinities just fine as long as you either a) bound them or b) keep them symbolic.
That only breaks down with the reals where equality is fundamentally incomputable. Equality of the rationals and approximate equality of reals is perfectly computable though, the latter meaning that you can get equality to arbitrary, but not actually infinite, precision.
…sometimes I do think that all those formalists with all those fancy rules about fancy limits are actually way more confused about infinity than freshman CS students.
Tlaloc_Temporal@lemmy.ca 4 months ago
Eh, if you need special rules for 0.999… because the special rules for all other repeating decimals failed, I think we should just accept that the system doesn’t work here. We can keep using the workaround, but stop telling people they’re wrong for using the system correctly.
The deeper understanding of numbers where 0.999… = 1 is obvious needs a foundation of much more advanced math than just decimals, at which point decimals stop being a system and are just a quirky representation.
Saying decimals are a perfect system is the issue I have here, and I don’t think this will go away any time soon. Mathematicians like to speak in absolutely terms where everything is either perfect or discarded, yet decimals seem to be too simple and basal to get that treatment. No one seems to be willing to admit the limitations of the system.
skulblaka@sh.itjust.works 4 months ago
That does very accurately sum up my understanding of the matter, thanks. I haven’t been adding on to any of the other conversation in order to avoid putting my foot in my mouth further, but you’ve pretty much hit the nail on the head here. And the higher mathematics required to solve this halting problem are beyond me.
ColeSloth@discuss.tchncs.de 4 months ago
If you can’t do it without fractions or a … then it can’t be done.
Bertuccio@lemmy.world 4 months ago
We’ve found a time traveller from ancient Greece…
WldFyre@lemm.ee 4 months ago
1/3=0.333… 2/3=0.666… 3/3=0.999…=1
ColeSloth@discuss.tchncs.de 4 months ago
Fractions and base 10 are two different systems. You’re only approximating what 1/3 is when you write out 0.3333…
The … is because you can’t actually make it correct in base 10.
WldFyre@lemm.ee 4 months ago
The fractions are still in base 10 lmfao literally what the fuck are you talking about and where are getting this from?
You keep getting basic shit wrong, and it makes you look dumb. Stop talking and go read a wiki.
myslsl@lemmy.world 4 months ago
What exactly do you think notations like 0.999… and 0.333… mean?
apolo399@lemmy.world 4 months ago
Sure, let’s do it in base 3. 3 in base 3 is 10, and 3^(-1) is 10^(-1), so:
1/3 in base 10 = 1/10 in base 3 0.3… in base 10 = 0.1 in base 3
Multiply by 3 on both sides:
3 × 0.3… in base 10 = 10 × 0.1 in base 3 0.9… in base 10 = 1 in base 3.
But 1 in base 3 is also 1 in base 10, so:
0.9… in base 10 = 1 in base 10
ytg@sopuli.xyz 4 months ago
Similarly, 1/3 = 0.3333…
So 3 times 1/3 = 0.9999… but also 3/3 = 1
Another nice one:
Let x = 0.9999… (multiply both sides by 10)
10x = 9.99999… (substitute 0.9999… = x)
10x = 9 + x (subtract x from both sides)
9x = 9 (divide both sides by 9)
x = 1
zarkanian@sh.itjust.works 4 months ago
My favorite thing about this argument is that not only are you right, but you can prove it with math.
ColeSloth@discuss.tchncs.de 4 months ago
Except it doesn’t. The math is wrong. Do the exact same formula, but use .5555… instead of .9999…
Guess it turns out .5555… is also 1.
WldFyre@lemm.ee 4 months ago
Lol you can’t do math apparently, take a logic course sometime
Let x=0.555…
10x=5.555…
10x=5+x
9x=5
x=5/9=0.555…
Reddfugee42@lemmy.world 4 months ago
Oh honey
pyre@lemmy.world 4 months ago
you have to do this now
SmartmanApps@programming.dev 4 months ago
Not a proof, just wrong. In the “(substitute 0.9999… = x)” step, it was only done to one side, not both (the left side would’ve become 9.99999), therefore wrong.
ytg@sopuli.xyz 4 months ago
The substitution property of equality is a part of its definition; you can substitute anywhere.
zarkanian@sh.itjust.works 4 months ago
They multiplied both sides by 10.
0.9999… times 10 is 9.9999…
X times 10 is 10x.