For the programmers: operator precedence.
Comment on A fake Facebook event disguised as a math problem has been one of its top posts for 6 months
jordanlund@lemmy.world 6 days ago
I’m sure we’re all geniuses here, but just in case…
Please excuse my dear aunt Sally.
Parenthesis, exponents, multiplication, division, addition, subtraction.
Why? Becauseca bunch of dead Greeks say so!
3x3-3÷3+3
(3x3)-(3÷3)+3
9-1+3
8+3
11
vext01@lemmy.sdf.org 6 days ago
Imgonnatrythis@sh.itjust.works 6 days ago
Not a genius. But if subtraction is last, why isn’t it 9-4?
aliceblossom@lemmy.world 6 days ago
Because its not really “1 plus 3”, its negative 1 plus 3 which is two. I know it seems a little weird but the minus sign is " tied" to the thing following it.
cecilkorik@lemmy.ca 6 days ago
Parenthesis, exponents, multiplication, division, addition, subtraction.
should actually be
Parenthesis, exponents, (multiplication and division), (addition and subtraction).
Addition and subtraction are given the same priority, and are done in the same step, from left to right.
It’s not a great system of notation, it could be made far clearer (and parenthesis allow you to make it as clear as you like), but it’s essentially the universal standard now and it’s what we’re stuck with.
iglou@programming.dev 6 days ago
No, it should simply be "Parenthesis, exponents, multiplication, addition.
A division is defined as a multiplication, and a substraction is defined as an addition. I am so confused everytime I see people arguing about this, as this is basic real number arithmetics that every kid in my country learns at 12 yo, when movong on from the simplified version you learn in elementary school.
13igTyme@lemmy.world 6 days ago
You want PEMA with knowledge of what is defined, when people can’t even understand PEMDAS. You wish for too much.
fluxion@lemmy.world 6 days ago
Addition/subtraction work out the dame regardless of how you order the operations. If you do subtraction last you have:
9-1+3
and you are adding 3 to the result of (9-1). Since you are trying to perform it before the (9-1) operation is carried out, you can add 3 to the 9:
12-1 = 11
or you can add three to the -1 and get:
9+2 = 11
You only end up with 9-4 if you were subtracting 3 rather than adding three. It all becomes more obvious if you read the original as:
9 + (-1) + 3
Geodad@lemm.ee 6 days ago
It’s multiplication or division from left to right followed by addition or subtraction, also from left to right.
That’s where a lot of people fuck up.
Mistic@lemmy.world 6 days ago
The “why” goes a little further than that.
In actuality, it’s because of fundamental properties of operations
- Commutation
a + b = b + a
a×b = b×a
- Association
(a + b) + c = a + (b + c)
(a×b)×c = a×(b×c)
- Identity
a + 0 = a
a×1 = a
If you know that, then PEMDAS and such are useless because they’re derived from those properties but do not fully encompass them.
barsoap@lemm.ee 6 days ago
Why? Because a bunch of dead Greeks say so!
The Greeks certainly didn’t come up with PEMDAS. US teachers too lazy to teach kids actual maths did. And that’s before taking into account that the Greeks didn’t come up with Algebra.
dohpaz42@lemmy.world 6 days ago
US teachers too lazy to teach kids actual maths did.
What’s lazy about learning PEMDAS? And what’s the non-lazy/superior way?
barsoap@lemm.ee 6 days ago
Learning the actual algebraic laws, instead of an order of operations to mechanically replicate. PEMDAS might get you through a standardised test but does not convey any understanding, it’s like knowing that you need to press a button to call the elevator but not understand what elevators are for.
Halosheep@lemm.ee 6 days ago
This guy is the the guy posting the answer and then spending hours fighting the idiots who got it wrong on Facebook.
Nerd.
AbidanYre@lemmy.world 6 days ago
Is it also lazy to learn Roy G. Biv to know the color spectrum instead of learning all the physics and optical properties behind that?
Or My Very Elderly Mother Just Served Us Nine Pickles to know the planets instead of learning orbital dynamics and astrophysics?
Christ man, it’s a mnemonic device for elementary schoolers.
dohpaz42@lemmy.world 6 days ago
You might be smart, but you’re still wrong about the importance of order of operations; especially in algebra.
As far as teachers go, you’re being a dick by generalizing all (US) teachers are lazy and do not understand math.
Pro tip: opinions are like assholes; you too have one, and yes it too stinks.
baines@lemmy.cafe 6 days ago
just say you like the smell of your own farts, it would be less text for us to read for the same result
datavoid@lemmy.ml 6 days ago
I’m a BEDMAS man myself
pulsewidth@lemmy.world 6 days ago
[deleted]jordanlund@lemmy.world 6 days ago
Multiplication and Division, and Addition and Subtraction are executed at the same level and done in left to right order.
pulsewidth@lemmy.world 6 days ago
[deleted]prole@lemmy.blahaj.zone 6 days ago
Because it’s just a mnemonic to remember what the order of operations is, not like… What the order of operations is, which you should know if you know the mnemonic.
Seasoned_Greetings@lemm.ee 6 days ago
Because it’s the only other thing about that system at all. OP wasn’t teaching, just showing what that system does. If you looked for a source that explains it you’d be told
czardestructo@lemmy.world 6 days ago
I guess remembering grade school order of operation means you’re a guinus now? Bar has gotten pretty low…
AnotherPenguin@programming.dev 6 days ago
And it will go even lower as people start relying mpre on AI…
SARGE@startrek.website 6 days ago
That’s the point.
Set the bar low, but just high enough that tons of people still trip over it.
Sit back and enjoy the comment wars.
The people who are confident but wrong are too proud to admit they were wrong even if they realize it, and comment angrily.
The people who are right and know why, comment for corrections and some to show off how S-M-R-T they are.
The people who are wrong but willing to accept that just have their realization and probably don’t think about it again. So do the people who don’t know and/or care.
But those first two groups will keep the post going in both shares and comments, because “look at all these wrong people”
It’s all designed to boost engagement.
Kusimulkku@lemm.ee 6 days ago
I like the version where these problems are made purposefully ambiguous so people will fight over it and raise the level of interaction
Ulrich@feddit.org 6 days ago
This right here is exactly why it’s been so popular for so long.
rigatti@lemmy.world 6 days ago
G U I N U S.
I know it’s probably a typo, but I’m enjoying it.
czardestructo@lemmy.world 6 days ago
I would like to say it was on purpose but it was not :( I might do math, spelling is not my forte.
dethedrus@lemmy.dbzer0.com 5 days ago
It’s jeenyus you moran!
All I can envision with your alternative is Whoopi Goldberg with a very fanciful hat serving drinks in space.