• gimpchrist @lemmy.world
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    3 months ago

    Nobody knows how to think like a dyscalculic at all haha… it’s just a little symbol thingy… it doesn’t have to be pi. Just like X is a little symbol thingy… the x is now just kind of a table right now… it’s just a little symbol thingy and it means five it’s not that difficult. Lmao

    • Agrivar@lemmy.world
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      3 months ago

      Here’s a little LPT for you: you can be correct without being an obnoxious douchebag about it.

    • nyctre@lemmy.world
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      3 months ago

      Yes it does have to be pi because that’s the formula for the volume of a cylinder. If you take a simple, cylindrical glass or container and measure it and apply the formula with pi, you’ll see that you’ll get the correct volume of the container. If you just want your kids to calculate a random x that’s 5* 10 *10 *10 just tell them to do that, don’t give them a made up formula, it’s not that difficult.

      • petrol_sniff_king@lemmy.blahaj.zone
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        3 months ago

        Mathematically, no, it does not. We make up the definitions. If you wanted to see what the consequences of a, I don’t know, 5-dimensional universe with Pi set to 5.65 were, you can do that. These are scribbles on pages, there is literally nothing stopping you.

        Academically, what’s stopping you is whether these calculations are useful. The only problem I see here is that it’s kind of misleading to imply to someone that Pi is something it conventionally isn’t. But even then, I think I’d respect the mathematician who could recognize Pi as a symbolic name for, usually, one particular transcendental constant a little bit more than one who refused to even entertain the idea. Like, imagination is important to mathematics, too.

        And to be clear, “let Pi = 3.14” is also incorrect. It is closer than 5, but it is still infinitely wrong.

        [edit] And also, I was imagining this question was for a younger audience. Reading it again, I’m not going to pretend I know what’s going on up there.

  • RegalPotoo@lemmy.world
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    3 months ago

    Idk, if you want to test people on how they understand formulae and order of operations without letting them just punch it into a calculator. The actual math isn’t hard, but if you don’t get substituting values into an equation then it’s not trivial

          • Norgur@fedia.io
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            3 months ago

            Oh don’t you try to sell me on the “you won’t always have a calculator in your pocket” thing. I have fucking Excel in my pocket.

            • notabot@lemm.ee
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              3 months ago

              It’s not just about haveing a calculator, it’s also that it’s faster and more convenient if you can do simple sums like this in your head. It also means you can sanity check the numbers your calculator gives you to make sure you didn’t make a mistake entering the sum.

              To your point below about products having their unit cost displayed, more than once I’ve seen that just be wrong, so I wouldn’t rely on it. Make sure you can check it in your head.

            • Serinus@lemmy.world
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              3 months ago

              Who really wants to use Excel to figure out if the 24-pack of Coca-Cola or the 3 12 packs is a better deal?

              • Norgur@fedia.io
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                3 months ago

                I don’t need to, there’s a legal requirement to print prices per liter or kg on every price tag here.

                • Gork@lemm.eeOP
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                  3 months ago

                  Does this requirement exist for toilet paper? Because I don’t know what the hell is considered a better deal based on all the marketing.

                • HopFlop@discuss.tchncs.de
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                  3 months ago

                  But if you want to buy only half a kg, you don’t know how much it costs (if you dont know basic maths)- because it only lists the price for a full kg. Do you start pulling out your Excel for that?

  • FiniteBanjo@lemmy.today
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    3 months ago

    I would be a smartass and leave Pi as a factor throughout and in the answer. I’m used to doing that in Calculus anyways.

    V = πr2h

    V = π⋅102⋅10

    V = π⋅100⋅10

    V = π1000


    BONUS SOLUTION:

    V =∫010 A⋅h dh

    A = ∫010 2πr dr

    V= ∫010010 h⋅2πr dr dh

    h is a constant for A’s integral so we can safely move it into V’s integral

    V= ∫010 h⋅∫010 2πr dr dh

    π is a constant so we can safely remove it from A’s integral

    A = π⋅∫010 2r dr

    A = π⋅[r2]010

    A = π⋅( [102] - [02] )

    A = π102

    A = π100

    V = ∫010 h⋅π100 dh

    π100 is a constant so we can safely remove it from V’s integral

    V = π100⋅∫010 h dh

    V = π100⋅[h]010

    V = π100⋅([10] - [0])

    V = π100⋅10

    V = π1000

    It goes a lot deeper but I’m not bored enough for that, yet.

    EDIT: Hang on. I’m wrong with that height integral. Can somebody help remind me?

    • benignintervention@lemmy.world
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      3 months ago

      If you really wanted to be through you’d start at a point, integrate out along dr for a line, then integrate in a circle through dtheta to derive the area before doing the rest