• klu9@lemmy.ca
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    14 days ago

    Some bureaucrats in Mexico City tried this years ago.

    An important ring road had two lanes in each direction. To increase its capacity, they didn’t actually widen the road; they just repainted the lane markings to turn two lanes into three, and claimed a 50% capacity increase!

    Everyone immediately screamed about being crammed together just centimetres apart, accidents increased and the city officials quickly u-turned; they repainted to have just 2 lanes in each direction again.

    But they then tried to claim that as that was a 33% decrease, and that because they had earlier increased it 50%, that meant they had achieved a net 17% increase in the road’s capacity!

  • MacN'Cheezus@lemmy.today
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    14 days ago

    TBF Yang really did write the equation in the sloppiest way possible.

    Like I know what he MEANS but no math professor in the world would let this shit slide.

  • adarza@lemmy.ca
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    15 days ago

    pegglegg back in fifth grade: ‘why i need to learn this math stuff. i aint never gunna use it’

      • adarza@lemmy.ca
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        14 days ago

        you still need to know what buttons to push on the magic box, and in what order…

          • nomy@lemmy.zip
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            14 days ago

            “It’s not like you’ll regularly have a little box in your pocket with access to the sum of all of the knowledge in the world but you’ll have to sift through an equal amount of incorrect knowledge and have the ability to differentiate the two.”

    • Bone@lemmy.world
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      14 days ago

      That kind of math didn’t start for me until letters started showing up in it. This is basic shit though!

  • dis_honestfamiliar@lemmy.sdf.org
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    14 days ago

    I might as well throw the same comment in here. You learn this pretty quickly when you bet on meme stocks. Down 90% then up 100% I can assure you, you are no where near where you started.

    • jonne@infosec.pub
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      14 days ago

      Same with crypto. You’ll get a notification something went down 10%, then up again 10%, but if you zoom out you see it’s just been slowly going down on average since the last huge spike.

    • jacksilver@lemmy.world
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      14 days ago

      This is clearly about the US stock market crashing. In that case it’s always the days gain/loss, in which case Yang is the only person who is right.

      This is important because a lot of people saw “down 10%” and now “up 10%” without realizing that’s still day over day loss.

  • JohnDClay@sh.itjust.works
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    15 days ago

    It’s only the same if it’s up 10% compared to the original number. It all depends on your time period, you could be up 30% compared to 7 years ago.

    • uranibaba@lemmy.world
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      14 days ago

      Tesla stock prices are good example of this. They are down ~50% since december and up ~70% since lowest point in april last year.

  • CheeseNoodle@lemmy.world
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    14 days ago

    Not even close to that anyway, the dow jones for example went from 44k to 37k back up to 40k. Still hasn’t even regained half the value it lost.

  • driving_crooner@lemmy.eco.br
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    14 days ago

    This is why in forecasting and time series analysis is used the log difference, a 10% increase or decrease on the log scale gives you the same value being added or removed.

      • driving_crooner@lemmy.eco.br
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        14 days ago

        Not really, you do t=n and t=n+1, for n= 1, 2, 3 for a quick view on volatility.

        Then ypu look up for correlations between e[t=n | t= 0, t= 1…] for different Ns. For more I would need to check out my notes

        • embed_me@programming.dev
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          14 days ago

          Oh I was imagining something entirely different. Like a simple logarithmic scale of a signal, I do not know anything about time series analysis. Should’ve kept my mouth shut

  • billwashere@lemmy.world
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    14 days ago

    Multiplication is commutative dipshits.

    A x B = B x A

    So 1.1 x .9 is always going to be .99, regardless of the order. Didn’t we learn this in like middle school?

    (Edit … to be clear I’m calling the people in the image dipshits, not the people commenting here).

    • phlegmy@sh.itjust.works
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      14 days ago

      Huh? We’re talking about percentages not multiplication. Where’d the 1.1 and .9 come from?

      • billwashere@lemmy.world
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        14 days ago

        If you increase something by 10% you’re doing this:

        (10% • X) + X

        (.1 • X) + X

        1.1 • X

        So you’re just multiplying the original value by 1.1. Similarly for subtracting 10% you’re multiplying by .9

        So the order in which you add or subtract 10% doesn’t matter. You always get the same number.

        • Ostrakon@lemmy.world
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          14 days ago

          I have 100 dollars. I lose 10% of it. I now have 90 dollars. Now I increase my 90 dollars by 10%. Is it your assertion that 10% of 90 is 10?

          • billwashere@lemmy.world
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            14 days ago

            No. Because increasing 90 by 10% is:

            90 • 1.1 = 99

            Percentage is relative to current value, not previous calculations. 10% of 90 is 9.