- cross-posted to:
- science_memes@mander.xyz
- cross-posted to:
- science_memes@mander.xyz
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To be Devil’s Advocate:
Given that the rest written in Comic Sans, it may be an early elementary school exercise, aimed at teaching kids to do multiplications. In this case, it’s tolerable and/or defensible to find a simplification for pi.That said, making pi equal to 3 would have been more accurate for that…
Or it’s from an ME. They seldom can remember the rounded value of Pi, but they’re pretty sure it’s somewhere between 3 and 4. But you probably should use 5 just to be safe…
Unless the kid is even slightly above average and finds the idea that pi equaling 5 confusing.
…if they’re above average, I think they’ll figure out the explicitly defined variable. I think the instructor is trying to make sure this problem doesn’t require a calculator and figured defining pi as 5 makes it clear that you can treat it as a whole number. 3 would be more accurate and just as easy, but meh idk that this is that great of a blunder.
You can be a smart kid and not realize that adults are lying.
I remember the Peas and the Punnett Square. Sure, mendelian genetics explains pea plant colors, but doesn’t explain dog fur colors. Just providing a footnote that more completed genetics exists would have been nice.
That’s a dumb way of teaching and you are a dumb devils advocate for saying it. Go to H E double hockey sticks.
Even in engineering it is common to just round pi to 3 and quickly estimate whatever it is your doing.
In astronomy, pi=1 or 10, depending on whether you’re trying to over or under estimate something. Because when you’re trying to estimate distances measured in millions of light years, the difference between 3 and 10 is just one or two orders of magnitude on a small number. It’s pretty common for astronomers to do napkin math by rounding every single number to the nearest zero. 91k becomes 100k for instance. Because the napkin math estimations are just trying to gauge whether some celestial event or object is a thousand light years away, ten thousand, a hundred thousand, etc… And pi becomes 10, because that’s the nearest round number.
Fermi Estimation. Where you’re dealing with something so big, you’re just interested in the magnitude.
Excuse me what? I’ve been an engineer for a decade and have never met anyone that would do that. We have calculators.
I think they mean napkin math. Like you’re in a meeting and they ask for a general idea if something will work or not
We all have phones with calculators, don’t really need to do napkin math anymore
Depends on the level of precision you need. If I want the volume in a 500 foot long, 3 inch pipe to roughly estimate how much supply I need to order, I wouldn’t need a calculator. It would very roughly be 90-95 ft3. (Divide 500 by 4 two times and multiple by 3)
Then I would spend 5 minutes double checking myself haha.
I suppose. I’m still internally outraged and haven’t run into such a situation before, but I accept this.
To be fair most of the situations where I’ve run into this have never involved pi, and sometimes it’s just qualitative.
That makes sense. I feel like if you’re at the point where pi is meaningfully involved, you should probably do your math.
I feel like a proper engineer would call only going two places past the decimal “rounding pie”.
I need a new maitre’d for a restaurant I am opening. How busy are you?
Not very, but I’ll require lots of pay.
How does 1 million a minute sound?
Ill take it!
I’ll give you the hardest 30 minutes I’ve worked in my life, and then retire.
So you do know how to act like a decent human. Damn. Well the restaurant closed. I guess you can just be nice for your own esteem now.
Nope. I had sold my house to move and told the kids already. Now I’m jaded I just lost out on 30 mill and we’re homeless. I’ll be an ass forever, now.
Pi is now 5 due to inflation
Damn inflation is everywhere now, even the transcendentals :'(
Having Pi equal five definitely does not help the world go round.
Wouldn’t it make it seem like a bigger place?
Maybe on paper if you want to look at it from that angle.
Tangentially, I like the pun, but now you’re just being obtuse.
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= ∫010 ∫010 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?
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
…in spacetime with high curvature?
Doesn’t curvature cause pi to not be a constant? And wouldn’t it be negative curvature that would cause it to be higher than euclidean space?
That’s how you know math is OP when you can calculate volumes in parallel worlds where circles don’t even looks like circles
Ah, Manhattan. Where pi = 4, and circles are diamonds.
Bringing new meaning to the phrase “assume cows are spherical”
“Assume a spherical cow, which for our purposes can be approximated as a cube.”
This is how the wealthy calculate their tax exemptions.
Due to inflation, they now have a bigger pi.
My favorite is when doing Order of Magnitude estimations, you are supposed to let pi = 1
They’re just rounding up from “3.”
pi, as it turns out, is just the friends we made along the way
Wow, 5 friends is more than what I have!
“One! Two! FIVE!” “Three, Sire!” “THREE!”
With π=5 maths break down completely. If π=5, then e^(5i) = -1, meaning -1 = cos(5) + i * sin(5), or -1 ≈ 0.284 - 0.959 i
I think you’re overthinking it. The first thing you’re told when you learn algebra is that a letter represents a number and you can say “let a equal (number), b equal (number)…” so you can let pi equal whatever you want for the purposes of one simple problem.
You’re talking about variables. But, pi isn’t a variable, it is a constant number. This would be more akin to saying “let 7 = 9”.
Or as I like to call pi…the little symbol thingy. But exactly yes, you get it.
Except pi isn’t a variable. It is a known value that we refer to as pi for convenience, and pi is a fundamental aspect of how a circle is. Saying “let pi equal 5” is all fine and well but is physically impossible, you will not be determining the volume of a cylinder if you let pi equal 5, because the ratio of a circle does not equal 5, it equals 3.14
Okay but they didn’t say 3.14 they made a little symbol thingy
Intel®️ inside
Wow, that takes me back - you’re referring to the floating point bug from …98?
500? But I just woke up and I take sleeping pills so my brain might not be working.
5*10**2*10 = 5*10*10*10 = 5000Good thing I don’t need to do math at work. Saw a video the other day where someone said “10x400” and was shocked that they couldn’t instantly multiply by a power of ten. And then I walked into this.
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
Just let π be 3 …
Or have them learn how to use a calculator at the same time.
Your life is easier and better if you can do this kind of simple math in your head.
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.
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.
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?
I don’t need to, there’s a legal requirement to print prices per liter or kg on every price tag here.
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?
