I always thought like that:
Hmmm: 1 + 2 + 3 + … + 99 + 100
Kommutativgesetz be like: This equals:
100 +1 + 99 + 2 +98 + 3 . . . And this equals: 101+ 101+ 101+ . . .How often do I need to do this? I use up 2 numbers for each 101. I have 100 numbers total. So that’s 50x101.
Now you can think about: What if it’s 1000 instead of 100? But it#s easy from here…
I’m a spatial-visual person, so when presented with this problem as a teenager, I instead solved it spatially. If you stack squares like.
█.
██.
███.
…To the hundredth row, you get a shape that is a half filled square that is 100x100. Except the diagonal is fully filled in, so you need to add another 50.
So the answer was 0.5x100x100 + 0.5x100. Easy to visualize, easy to solve. 5050.
There’s a similar problem in sports – I was a teaching assistant for our rural school’s gym class so this one also popped up for me as a teenager. If you have 100 teams and each team needs to play each other team once… You fill in a similar grid, with the teams on both the x and y axis. The diagonal gets removed in this scenario because a team cannot play itself. So the answer is 0.5x100x100 - 0.5x100. 4950. Anyone who has ever tried to plan any sort of tournament can probably solve this intuitively, but 25 years ago I though I was the smartest gym class teaching assistant ever ;)
This is why I never succeeded at math. Like why does this shit work?? How can people just take a problem and be like, nah I’m going to just throw numbers all over the place and reassemble them in all sorts of ways and get an answer somehow…
I can’t just memorize arbitrary nonsense that “just is” I need to know how it works or it never sticks and all the math I’ve ever been taught was just “memorize this arbitrary nonsense and regurgitate a specific formula for a specific application that we’ve spent 0 time explaining other than telling you to memorize it. You want proofs and you can’t get proofs until advanced college courses” well guess I’ll just never understand mathematical manipulation then…
I feel like 50/50 school failed me and I failed at math.
You were failed by people who didn’t help you learn intuitions and instead caused you to focus on memorization.
It’s not arbitrary. Really try to think about the problem at hand. The ‘why’ is quite apparent. Ask yourself why did they go with 99+1+98+2… in the first place? And why is that the same as 101+101…? What was the benefit of simplifying it to that? How did it save the student time?
You can deduce this yourself and literally no memorization is involved to figure this out. No formulas needed either.
It’s just a matter of breaking the problem down Into an easier problem or set of problems.
All the additions are interchangable, so you could choose to add 1+2+3+4 or 4+1+2+3 and then 4+1=5 and 2+3=5 and then youve got 5+5 which is easy its 10. So you go ok you can do the conversion with 1 and 50 except it’s still tough mental math so you say 1 and 100 to get 101 100 times, but that’s twice too big so you slap it in half and you get the answer. It’s solving a tough problem by splitting it into problems that aren’t as tough.
The first step is knowing what tools you have in your belt. The second is knowing how they work in detail. The third part is the inspiration of using them in a way that solves a difficult problem.
I’m not a mathematician, but I’ve found interesting solutions to problems like this before, and it’s fun when you understand your tools and understand the problem and it all comes together to find a solution nobody else would have.
The rules underpinning math are axioms in the end, but they’re not completely arbitrary, because if you change them in most cases it just fucks everything up.
The axioms that were chosen were chosen for good reason, and the rules they result in (such as summation and multiplication being commutative so 3x4=4x3 and 3+4=4+3) allow more complex rules to be created.
There’s a lot of philosophy of math at the core of all this , but it’s not really true that this is all arbitrary.
Can also be called a programmer move
Not a good one.
Better than a regular grammer move
Just put it in the calculator.
… am I the only one who learned 1+100, 2+99… to make 101 times 50 pairs? Lmao feels like it’s much easier. 101 × 50 = 5050
The math is the same, you just wrote it more “casually”. For me it was 0+100, 1+99, 2+98 … 49+51 -> 100 x 50 = 5000, then add the 50 that was missed from the middle for 5050. But yeah I remember coming up with that when I was really young.
Sorry if this is stupid but how to deal with sums to odd numbers ? Won’t you have a number left over after pairing all the others?
Nope, because what you’re doing is copying the entire sequence, reversing it, and pairing up each element left to right. There’s no way to have any leftovers because the original sequence and the new reversed sequence have the same number of elements.
A perhaps less intuitive way of thinking of it is you start with a sequence of 1 up to N, which contains exactly N elements. The sequence from 1 to N and its reverse together contain 2N elements, which is by definition an even number, regardless of whether N is even or odd. Because it’s even we can break it into pairs without leftovers.
Pythagoras ▄︻デ══━一 Gauss
Edit: Oops, that doesn’t quite work without specifying why it obviously needs to be a 101 by 100 triangle, which I can’t do on weed. Something about 1 side including 0-100 maybe?
That seems complicated.
Average is (100+1)÷2= 50.5
50.5 average x 100 numbers = 5050.
You did essentially the exact same thing in a different order.
(100+1)÷2 × 100
(100+1)x100 ÷ 2
Clever though
The neat thing about math is that you can generally find several different paths to the same solution, and go with whichever is most intuitive to you.
I never made it far enough in math to understand this.
Addition?
Seeing this meme gives me flashbacks to the 10 Deutschmark bill (I think that was the one)
I thought it was Euler that did this. But I can imagine Gauss doing it too.
Ahh because Euler did everything
