this post was submitted on 27 Apr 2025
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[–] stebo02@lemmy.dbzer0.com 74 points 4 days ago* (last edited 4 days ago) (7 children)

you can trucate it and it still only a slightly worse approximation:

987/123 = 8.024

98/12 = 8.167

9/1 = 9.000

The last one is pretty bad you should probably not use it

[–] OutlierBlue@lemmy.ca 37 points 4 days ago (1 children)

9/1 is approximately 8, for extremely large values of 8.

[–] toynbee@lemmy.world 4 points 3 days ago

Hello, fellow old nerd.

[–] JackbyDev@programming.dev 32 points 4 days ago
[–] somedev@aussie.zone 17 points 4 days ago (2 children)

For that last one, how bad are we talking? I need to know soon, I have some important banking software I need to develop.

[–] stebo02@lemmy.dbzer0.com 14 points 4 days ago

I wouldn't use it for precise calculations at NASA, but for banking stuff I think it would be fine :)

[–] prole@lemmy.blahaj.zone 3 points 4 days ago

It depends on the scale of the thing you're using it for.

[–] pacology@lemmy.world 12 points 4 days ago

Have you considered running for Indiana governor? You have the right mindset.

https://en.wikipedia.org/wiki/Indiana_pi_bill

[–] Neverclear@lemmy.dbzer0.com 8 points 3 days ago (2 children)

Nah, the engineer probably designed it with a safety factor. You could probably even go 9/0 and be perfectly safe ;)

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[–] stebo02@lemmy.dbzer0.com 8 points 4 days ago* (last edited 4 days ago)

By the way guys, a very similar approximation for 8, which also starts at 9.000 for n=1, but quickly gets much closer to 8 for increasing n, is:

exp{-2(n-1)} + 8

It approaches 8 about as fast as the above method but this one has a simple formula that is usable in python etc.

[–] humanspiral@lemmy.ca 3 points 3 days ago

16/2 is an almost exact replacement for 8. OP's name includes Fermat, and so he's probably smarter than me though.

[–] grrgyle@slrpnk.net 77 points 4 days ago (9 children)

Shit like this makes me realise why people become mathematicians. You just play around with numbers and find funny facts about them.

[–] driving_crooner@lemmy.eco.br 50 points 4 days ago* (last edited 4 days ago) (1 children)

So, years ago in college in Linear Algebra our professor said to us to study about idempotent matrices. So I checked out that wiki page and saw the example for 2x2 matrix, that are composed by the numbers 3, -6, 1 and -2. And I was like wait a second, 3×-2=-6 there's no way they are not relationship there, so I started trying other numbers, and found and proved (using induction) that any n, -n(n-1), 1, -(n-1) is an idempotent matrix. At the test there were no questions about that, and I was short of 0.5 poits to pass the class without having to present a final exam and I told my professor that I spent a lot of time learning that and that even discovered something and proved he pass me the chart and asked me to proved it, after that he gave the missing points. Was really good.

[–] Kusimulkku@lemm.ee 5 points 4 days ago (1 children)

You need to put the name inside the brackets and the link inside the parentheses.

idempotent matrices

[–] GraniteM@lemmy.world 15 points 4 days ago (1 children)

I myself once learned 380 digits of π, when I was a crazy high-school kid. My never-attained ambition was to reach the spot, 762 digits out in the decimal expansion, where it goes "999999", so that I could recite it out loud, come to those six 9s, and then impishly say, "and so on!"

—Douglas Hofstadter

[–] grrgyle@slrpnk.net 5 points 4 days ago (1 children)

That would be an amazing party trick.

[–] grrgyle@slrpnk.net 5 points 4 days ago (5 children)

Actually come to think of it, even more amazing in the age of smart phones, when it's possible to easily verify to numbers you're reciting.

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Then you try to figure out why they do be like that

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[–] match@pawb.social 46 points 4 days ago (7 children)

gonna need this in every base

I'll start with base 2:

1/1 = 1

[–] mattd@programming.dev 16 points 4 days ago

Base 3:

21 / 12 = 1.1012101210121012

[–] MelodiousFunk@slrpnk.net 10 points 4 days ago (1 children)

gonna need this in every base

...all of them?

[–] match@pawb.social 3 points 4 days ago

for great justice

[–] LeninOnAPrayer@lemm.ee 8 points 4 days ago

I'm gonna need a formal proof for this.

[–] PattyMcB@lemmy.world 6 points 4 days ago

We should be friends

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[–] Robust_Mirror@aussie.zone 22 points 4 days ago (2 children)

987654312÷123456789

Change the 21 at the end of the first number to 12 and its perfect. It was only ever 9 away.

[–] shekau@lemmy.today 12 points 4 days ago
[–] edgemaster72@lemmy.world 9 points 4 days ago* (last edited 3 days ago)

Witch! Begone foul demon, and take your dark sorcery with you!

[–] rainrain@sh.itjust.works 33 points 4 days ago (1 children)

I just noticed what the numbers are. It really is easy to memorize. So convenient.

Unfortunately, it requires remembering 8, so it kinda defeats the purpose.

[–] FooBarrington@lemmy.world 10 points 3 days ago (1 children)

You may call it an approxim8ion

[–] BodilessGaze@sh.itjust.works 2 points 3 days ago

gr8 m8, I r8 8/8

[–] PattyMcB@lemmy.world 20 points 4 days ago

The funniest part is that some people will never understand the absolute crusade that some mathematicians might fight over this one day

[–] Hjalamanger@feddit.nu 14 points 4 days ago

9876543210987654321 / 1234567890123456789 = 8,0000000729000

[–] deegeese@sopuli.xyz 16 points 4 days ago (2 children)

I wonder if there’s a related infinite sequence which converges on 8?

[–] moonlight@fedia.io 21 points 4 days ago (1 children)

This sequence approximates an integer to arbitrary precision, not 8 specifically though, and never perfectly.

I tried it out using other bases, and the rule seems to be that doing this in base n results in n-2 with remainder n-1. So it doesn't ever actually converge, but the remainder becomes small very fast.

[–] match@pawb.social 11 points 4 days ago (2 children)

never perfectly

eyes you in binary

[–] deegeese@sopuli.xyz 11 points 4 days ago (1 children)

The sequence in base 2 is only 1/1.

Wonder how close base-16 gets.

FEDCBA987654321 / 123456789ABCDEF

[–] moonlight@fedia.io 10 points 4 days ago

Off by '1.82959E–16' !

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[–] Rusty@lemmy.ca 4 points 4 days ago

(n * 8 + 1) / n

[–] Hupf@feddit.org 2 points 3 days ago
[–] thedeadwalking4242@lemmy.world 5 points 4 days ago* (last edited 4 days ago) (2 children)

It contains the number 8 though. So how is that useful

[–] Opisek@lemmy.world 4 points 4 days ago

Well, simple. Jest substitute that 8 with the above approximation.

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[–] expatriado@lemmy.world 5 points 4 days ago (1 children)
[–] moonlight@fedia.io 12 points 4 days ago

See my other comment, it's no coincide– there's a pattern. I would love to see an actual proof for it though, I don't know enough to say why it behaves that way.

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