This is quite possibly the best maths joke I've ever seen.
[edit] I guess it still can't beat the 'be rational' / 'get real' one.
this post was submitted on 19 Jun 2025
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You got the wrong symbol in the headline, it should be >3
25 - ⁵/₅ = 25 - 1 = 24
If you wrote it vertically: 25 - 5 ————— = 24 5
But once you lay it out on one line, you have to use prins to prioritize addition / subtraction:
(25 - 5) / 5 = 20 / 5 = 4
Some YouTube mathematicians deep-dive into this.
Yeah and 24 = 4 factorial = 4!
The joke is 4! (Factorial) Is 24 so it looks right even if you do order of operations incorrectly.
Ok so I'm not dumb! Usually I am with math but I got this one. Go me!
Comment section full of people looking for an opportunity to argue
No it isn't
Yes it is
Wait, will this be the 5-minute or the half hour?
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5-5/5 != 4
4 != 24 but also
4! = 24
4! = 5-5/5
5-5/5 != Sandwich
I understand why this is wrong (order of operations dictates the division happens first, so it's really 25 - 1 = 24), but why is it funny? I don't mean "This isn't funny," I think I'm just missing the joke.
4! Is meant to be 4 factorial. 4! = 4 x 3 x 2 x 1 = 24
The fuck is a "factorial"? They didn't teach me that one in high school math and I couldn't afford college.
Factorial means n! = (n)(n-1)(n-2)... etc. down to 1, where n is a positive integer. It's used to calculate the different number of configurations of a set of elements, mainly in combinatorics.
Like if you have four different objects and you want to know how many different configurations you can order them in, you have four choices for the first object, then three for the second, then two for the third, then one for the final slot. So the answer is 4 x 3 x 2 x 1 = 24 = 4!.
What's the point of factorials?
Makes things shorter.
In the applications mentioned by other people, you run into calculations that would look really messy and confusing. Things like 5•4•3•2•1 can be shorted to just 5! Imagine writing the full version of 123!
They're used in permutations and combinations a lot. Combinations is pretty obvious based on the name. Given X things, how many ways are there to choose Y. Permutations are the same but where order matters.
For example, if you shuffle a deck of cards properly randomly there will be 52! possible orderings (permutations).
There are lots of applications, so I’ll give you three
Factorials are used in the Taylor Series to approximate trigonometric (sine, cosine, etc) and the exponential function. This can help speed up calculations.
In probability and statistics, if you want to find how many different ways a deck of cards can be shuffled, the answer is 52! Because the first card can be any of the 52, the second can be any of the remaining 51, and so on until the last card. Building upon this concept results in ways to model data like the binomial distribution , which is simply “how many successes will i get if i do this trial a certain number of times”. E.g. If I flip a coin 100 times, how many times will it be heads?
In computer science, the complexity of a program is compared to functions like the factorial, exponential, quadratic, etc. to visualize it’s performance given the size of the input, n. E.g. a program of linear time complexity is denoted as O(n), and as n increases, we expect the time for the program to finish to increase linearly. For a factorial time complexity, O(n!), we expect the time to complete to increase a lot compared to O(n)
Im sorry your highschool curriculum failed to teach you. I learned factorals in jr highschool
Aha! Got it, thank you so much.
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4! = ...Wait, that's literally the point of the post this time
ASCII hack failure of language. Even in mathematics, ! has multiple meanings like with Boolean NOT. We need a science, math, and language reformation to remove non intuitive narcissistic names, and implied contextual meanings.
I've never seen ! used for boolean NOT in maths, just ¬. I think ! is something programming languages went for because it's easier to type. That said, screw (a, b). Is that a (coordinate) pair, an interval, an inner product, some secret fourth thing? Who knows!
Inner products are written as ⟨a,b⟩, no? Fair point on the interval, tho
I believe you mean, "nice pun!"
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