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 4 weeks 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 4 weeks ago
Imgonnatrythis@sh.itjust.works 4 weeks ago
Not a genius. But if subtraction is last, why isn’t it 9-4?
aliceblossom@lemmy.world 4 weeks 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 4 weeks 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 4 weeks 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.
SmartmanApps@programming.dev 1 day ago
A division is defined as a multiplication
No it isn’t. Multiplication is defined as repeated addition. Division isn’t repeated subtraction. They just happen to have opposite effects if you treat the quotient as being the result of dividing.
13igTyme@lemmy.world 4 weeks 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 4 weeks 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 4 weeks 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 3 weeks 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 4 weeks 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 4 weeks 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?
SmartmanApps@programming.dev 1 day ago
What’s lazy about learning PEMDAS?
Nothing. Only people who don’t know what they’re talking about say that.
barsoap@lemm.ee 4 weeks 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 4 weeks 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 4 weeks 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 4 weeks 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 3 weeks 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 4 weeks ago
I’m a BEDMAS man myself
pulsewidth@lemmy.world 4 weeks ago
[deleted]jordanlund@lemmy.world 4 weeks ago
Multiplication and Division, and Addition and Subtraction are executed at the same level and done in left to right order.
pulsewidth@lemmy.world 4 weeks ago
[deleted]prole@lemmy.blahaj.zone 4 weeks 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 4 weeks 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 4 weeks ago
I guess remembering grade school order of operation means you’re a guinus now? Bar has gotten pretty low…
SARGE@startrek.website 4 weeks 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 4 weeks ago
I like the version where these problems are made purposefully ambiguous so people will fight over it and raise the level of interaction
SmartmanApps@programming.dev 1 day ago
None of them are ambiguous. They all have only 1 correct answer, just like this one only has 1 correct answer. They all test if people remember the order of operations rules. Those who got it wrong, don’t.
Ulrich@feddit.org 4 weeks ago
This right here is exactly why it’s been so popular for so long.
AnotherPenguin@programming.dev 4 weeks ago
And it will go even lower as people start relying mpre on AI…
rigatti@lemmy.world 4 weeks ago
G U I N U S.
I know it’s probably a typo, but I’m enjoying it.
czardestructo@lemmy.world 4 weeks 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 3 weeks 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.