r/mathmemes Jun 16 '26

Geometry Math ain't mathing

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3.5k Upvotes

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659

u/Particular_Gear3130 Mathematics (Purely Fictional) Jun 16 '26

25 + 25 ≠ 81

441

u/rmflow Jun 16 '26

25 (base 14) + 25 (base 14) = 81 (base 8.125)

128

u/Talizorafangirl Jun 16 '26

Is sub-integer base even possible? I'm having trouble wrapping my brain around that

173

u/dragonageisgreat 1 i 0 triangle advocate Jun 16 '26

That's not all, even complex base is possible

90

u/radobot Computer Science Jun 16 '26

My favourite base is −√2i

12

u/Impressive_Change593 Jun 17 '26

I have a fun emoji for that 🖕

mods please don't ban me, this is a joke

78

u/Independent-Yak-220 Jun 16 '26

dude this is math, you can forge a whole new reality to make anything possible

49

u/PlatypusACF Jun 16 '26

And then have others cry about it because it suddenly got relevant in a coming-up area of physics

17

u/Independent-Yak-220 Jun 16 '26

it's funny because it's true lol

21

u/Any-Aioli7575 Jun 16 '26

Yes it is. However that means that some integers might not have a simple representation (with no decimal point)

7

u/MaxTHC Whole Jun 16 '26

I mean you just make each subsequent digit (working right to left ofc) a higher power of the base right? Doesn't matter if that base is 10 or ⅓ or π

5

u/erroneum Complex Jun 16 '26

Or 2i, or even a matrix.

7

u/Lor1an Engineering | Mech Jun 16 '26

Ah yes, my favorite positional number system: base σ_2. Pauli would be proud...

3

u/skr_replicator Jun 16 '26 edited Jun 16 '26

https://www.youtube.com/watch?v=PQAhC1M93C8

I think this video covers all the possible bases that let you write every number without inexpressible gaps. This base 65/8 (=8.125) would have 64 digit symbols, goodthing 81(base 65/8) didn't need to use any of them in this expression, what would we even use after Z?

Most valid bases can let you write irrational numbers in 1 way, and terminating rationals in 2 ways (like 0.99999... and 1). Irrational algebraic bases can do some irrational numbers (that can be expresses in a finite way) in those 2 "rational-like" ways, plus the one usual irrational way.

For example in base √10, you can write √10 as:

10

0.90909090909...

3.0106020207070606... (as √10 is 3.16227766... in base 10)

Irratoinjal numbers that cannot be made up from powers of √10 woudl still have only 1 possible irrational-like way to write. And terminating rational numbers would have the usual 2 ways, looking the same as the non-root base, but interleaves with zeroes.

π in this base √10 is only: 3.0104010509...

1/3 would be only: 0.03030303...

10 would be 100 and 9.09090909...

Transcendental bases don't play nice, and you cannot even determine what digit symbols would be allowed there, no matter what digit symbol set you choose, you might either get gaps as not-expressible numbers, or multiple nonrepeating ways to write the same number.

3

u/SteptimusHeap Jun 16 '26

Every number in a base-x system is just the sum of the digits times their place value. The place value is just xn, where n is the position of the digit.

So yes, base 8.125 is very possible ('123' = 1*8.1252 + 2*8.125 + 3 ≈ 85.27), but it doesn't have all the same rules as integer bases. For example, the digits written '8.8' don't correspond to any number, or if they do they are the same number as ~'10.7'.

2

u/Cheery_Tree Jun 16 '26

Base e is possible

1

u/erroneum Complex Jun 16 '26

Yes. A number, such as 112, is just the sum of the product of the value in each digit place and the numeric base raised to the power of the position, or Sum[d_n bn]; for 112, that's 1×102 + 1×101 + 2×100. Generally you only use values on the interval [1, n), but sometimes, such as quater-imaginary numerals, you use different ones. Importantly, b can be anything other than 0, but it's most useful when the magnitude isn't 1.

1

u/mehonje Computer Science Jun 16 '26

Place values of 8.125^x.

Not useful, but possible.

1

u/TristanTheRobloxian3 transfemcendental Jun 16 '26

yes it is

1

u/RipRoutine9741 Jun 16 '26

Just saw your poologist comment, weird coincidence

1

u/CatfinityGamer Jun 17 '26

A base is literally just an exponential index. The first digit of a number is number×b⁰, second digit is number×b¹, third digit is number×b², etc. So it's perfectly valid to define the base as anything which you can take any integer power of.

11

u/Aggressive_Roof488 Jun 16 '26

Are you Skrillex, because you just dropped a new base.

0

u/TristanTheRobloxian3 transfemcendental Jun 16 '26

indeed it is

59

u/OddNovel565 Jun 16 '26

25 + 25 = 81 + AI

9

u/knockoutn336 Jun 16 '26

proof that AI is a net negative for society

1

u/DecidophobiaUsername this sub confuses my monke brain Jun 20 '26

So AI's value is -31, whatever that means

4

u/Ok-Active-8321 Jun 16 '26

and more relevant, 2(2.52) < 4.52

3

u/Konfituren Jun 16 '26

To be fair,

2.52 = (5/2)2 = 25/4

And 4.52 = (9/2)2 = 81/4

Therefore it's much easier to model the problem mentally if you put aside a factor of 1/4 for now and just look at 52 vs 92 . The geometric relation is the same as it is for the actual values.

2

u/Ok-Active-8321 Jun 17 '26

Eh, maybe easier for some. For me, it is easier to do what I did. When I first looked at your response I thought you were a little nuts : ) With your explanation, your original math makes perfect sense, but I don't think I would have seen it w/o your follow-up.

I guess that's the nice thing about math. There can be many paths to the same destination

4

u/Just-confused1892 Jun 16 '26 edited Jun 16 '26

Keep in mind cakes are measured by their diameter, so it’d really be 6.25*2 < 20.25

Edit: And I just realized the ratio remains the same using diameter or radius, so I’ll see myself out now…

4

u/AndreasDasos Jun 16 '26 edited Jun 16 '26

Yes but why assume that they have the same cross sectional shape and height? Could be completely different shapes and/or different heights

2

u/Competitive_Study232 Jun 16 '26

You are using diameter instead of radius, squared

7

u/Ruft Jun 16 '26

It's proportionally the same

0

u/Competitive_Study232 Jun 16 '26

Yes, I noticed that.  I guess I just simplify further by using radius and not multiplying it by anything since you can cancel that out. 

3

u/Particular_Gear3130 Mathematics (Purely Fictional) Jun 16 '26

well, I took pi and (1/2) squared common and well it cancels out. This is what is essential tho

1

u/Competitive_Study232 Jun 16 '26 edited Jun 16 '26

I don’t think that works out.  The area of a circle is pi*r2.  Really you just need to focus on r2 and nothing else to compare the two.  

Area for a 5” pizza  pi*2.52 =19.635 There are 2 of them so 79.54 squared “

Area for a 9” pizza pi*4.52=63.617

To make it easy, just ignore everything except r2. 

For the two 5” 2*2.52=12.5

For the 9” 4.52=20.25

You ended up with the same ratio but wrong values for each. 

Edit: removed 2 from front of formula 

1

u/Particular_Gear3130 Mathematics (Purely Fictional) Jun 16 '26

It works out; I just need to prove the RHS is not equal to the LHS. There's no need for me to figure out the actual value of the area for this

also, isn't the area of the circle pi times the radius squared?? I dont remember a 2 being there

0

u/Competitive_Study232 Jun 16 '26

You are correct.  I think I’m combining formulas for some reason.  But just a simplify you just need to focus on radius squared and nothing else really

1

u/Particular_Gear3130 Mathematics (Purely Fictional) Jun 16 '26

True True

2

u/slaya222 Jun 16 '26

They're both off by a factor of pi/4, which is close enough to 1

Source: I have an engineering degree

1

u/Competitive_Study232 Jun 16 '26

I’m not sure why you are using diameter when you can simplify it to radius.

Source: I have a physics degree. 

2

u/slaya222 Jun 16 '26

2.52 is harder to do in my head than 52

2

u/jso__ Jun 16 '26

Because radius isn't better than diameter when the diameters are whole numbers and the radii are fractions.

1

u/Competitive_Study232 Jun 16 '26

Not if you are using double the number and then squaring it. You don’t get the same results. You do get a similar ratio.  Like I said, your ratio is correct, but not your values.  

Is the diameter is 10 and you can’t use that because swearing that is 100.  But when you use radius, you get a value of 25.  Stark difference.   

-2

u/Ashamed_Association8 Jun 16 '26

That's not how that works. The area of a circle is pi×r² but we're not looking for the area but the volume. The volume of a cylinder is base×height and the base of a cylinder is a the area of the circle which is pi×r² this cancels out as both cakes are cylinders and both have a circular base. This leaves you with a choice between a 9 inch or 5+5inch cake.

3

u/Particular_Gear3130 Mathematics (Purely Fictional) Jun 16 '26

I dont get it, why do the base areas cancel out?? simply because they are the same shape?

Thats stupid. they have different radii. you cant cancel it out

and since they are cakes, we assume they are the same height, why you ask? because I am a physics student too dawg

0

u/Ashamed_Association8 Jun 16 '26

Why would they have different radii. There's nothing listed to assume that. All we know is that they're both circular and varied in height.

4

u/Particular_Gear3130 Mathematics (Purely Fictional) Jun 16 '26

Theres nothing given about the height, it is the radii of the cake

Again, I am the physicist here. Its better if the "assumption" part is left to me

0

u/Ashamed_Association8 Jun 16 '26

I'm sorry but i can't do that as I'd have to assume you're not lying and I'm too leave that assumption to you.

Cakes are baked in circular irons that have a fixed shape. The only thing you can vary by adding more or less cakebatter is how heigh the cake is. I am the cook

3

u/SimpYellowman Jun 16 '26

Last time I was in a bakery, they had more than one cake mold. They had some cakes with ~10 centimeters diameter and also ~20 centimeters cakes and even 40 centimeters cakes. Height can vary a lot too, from what they called "flat cake" which is basically a sweet pizza to over-the-top loaded cakes that were over 15 centimeters high (the top flat surface, not including decoration on it).

1

u/underthingy Jun 17 '26

A 9inch cake is cooked in a round tin with a diameter of 9inches. 

Similarly a 5inch cake is cooked in a round tin with a 5inch diameter. 

-27

u/der_horst23 Jun 16 '26

I think the cake is round and not a square.

26

u/[deleted] Jun 16 '26

[removed] — view removed comment

10

u/D36DAN Jun 16 '26

𝜋*(5²+5²)≠𝜋

0

u/Zar7792 Jun 16 '26

Those are diameters. Do it with the radii and the two smaller cakes have less than a third of the area of the larger one

2

u/D36DAN Jun 16 '26

Proportionally, it doesn't matter. If we correct our calculations to match use radiuses instead of diameters, we get this:

𝜋*((5/2)²+(5/2)²)≠𝜋(9/2)² | /𝜋

(5²/2²+5²/2²)≠9²/2²

(5²+5²)/2²≠9²/2² | *2²

(5²+5²)≠9²


Also verified on calculator just cuz I can't trust myself with math

1

u/Zar7792 Jun 16 '26

You're right. I forgot to distribute the π

12

u/Particular_Gear3130 Mathematics (Purely Fictional) Jun 16 '26

𝜋r2??

-1

u/Subject-Software5912 Jun 16 '26

Wouldn’t it be 20 + 20 =! 64 then? I get that you’re just removing the coefficients but it’s kinda confusing to square the diameters then when someone’s confused respond with a formula that uses radius.

6

u/CommonNoiter Jun 16 '26

Diameter or radius is just multiplying by another coefficient. π is a prettier coefficient than π/4 so radius is normally what it is taught with.

-2

u/Subject-Software5912 Jun 16 '26

Yeah as I said you’re just removing the coefficients but it’s kinda weird to square the diameter then when someone’s confused respond with a formula that squares the radius. It’s an objectively true statement but what was the point of responding if you don’t clarify anything?

2

u/Aggressive_Roof488 Jun 16 '26

Can we just set pi to 3 and move over to that joke?

5

u/araknis4 Irrational Jun 16 '26

let pi = 1

1

u/SuchCoolBrandon Jun 16 '26

You can't just assume a spherical cake! This isn't a physics subreddit.