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submitted 6 months ago by fossilesque@mander.xyz to c/science_memes@mander.xyz

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[-] Tarquinn2049@lemmy.world 12 points 6 months ago

There is a bit of a typo in it. Since the list of 100 numbers was split in half, it should be x50 not x100. 50 sets of 101 from each pair.

[-] thatsTheCatch@lemmy.nz 37 points 6 months ago* (last edited 6 months ago)

It's not split in half, it's reversed, which is why both are equal to S. If you just took half, then 1 + 2 + ... would not equal 100 + 99 + ... and so they both wouldn't be equal to S.

Instead of halving the list, they just reversed it and summed it to 2S later, which they then half. So no typo here.

[-] bisby@lemmy.world 17 points 6 months ago

I had the same reaction originally though, because I feel like I had seen this previously as just "bending" the list of 1-100 in half.

1+2+3+4+...+49+50
100+99+98+97+...+52+51
=
101+101+101+...

101 * 50.

So you have to do a bit more thinking to define your equation but the equation takes you straight to S instead of 2S.

And since the meme just has + ... instead of showing where the end of the list was, I see how one could easily mix up the 2 approaches.

[-] Aceticon@lemmy.world 24 points 6 months ago* (last edited 6 months ago)

2S = 100 sets of 101

hence

S = 100/2 sets of 101 = 50 sets of 101 = 5050

I wondered about the same thing so did the Maths (which is kinda the point of the meme) back from 5050 and it all checks out.

[-] Tarquinn2049@lemmy.world 2 points 6 months ago

Oh ok. Yeah fair. I guess I'm used to the simplified version. Where it doesn't use the full list, just splits it in half. This method would also work for odd lists of numbers rather than only even. Makes sense.