I stand corrected
Comment on A fake Facebook event disguised as a math problem has been one of its top posts for 6 months
HereIAm@lemmy.world 3 weeks agoSo let’s try out some different prioritization systems.
Left to right:
(((6 * 4) / 2) * 3) / 9
((24 / 2) * 3) / 9
(12 * 3) / 9
36 / 9 = 4
Right to left:
6 * (4 / (2 * (3 / 9)))
6 * (4 / (2 * 0.333…))
6 * (4 / 0.666…)
6 * 6 = 36
Multiplication first:
(6 * 4) / (2 * 3) / 9
24 / 6 / 9
Here the path divides again, we can do the left division or right division first.
Left first:
(24 / 6) / 9
4 / 9 = 0.444…
Right side first:
24 / (6 / 9)
24 / 0.666… = 36
And finally division first:
6 * (4 / 2) * (3 / 9)
6 * 2 * 0.333…
12 * 0.333… = 4
It’s ambiguous which one of these is correct. Hence the best method we have for “correct” is left to right.
vithigar@lemmy.ca 3 weeks ago
SmartmanApps@programming.dev 1 day ago
I stand corrected
No, you weren’t. Most of their answers were wrong. You were right. See my reply. 4 is the only correct answer, and if you don’t get 4 then you did something wrong, as they did repeatedly (kept adding brackets and thus changing the Associativity).
Melvin_Ferd@lemmy.world 3 weeks ago
Maybe I’m wrong but the way I explain it is until the ambiguity is removed by adding in extra information to make it more specific then all those answers are correct.
SmartmanApps@programming.dev 1 day ago
until the ambiguity is removed
There isn’t any ambiguity.
all those answers are correct
No, only 1 answer is correct, and all the others are wrong.
Until the author gives me clarity then that sentence has multiple meanings. With math
Maths isn’t English and doesn’t have multiple meanings. It has rules. Obey the rules and you always get the right answer.
it doesn’t click for people that the equation is incomplete.
It isn’t incomplete.
Melvin_Ferd@lemmy.world 1 day ago
Can you explain how that is? Like with an example?
SmartmanApps@programming.dev 1 day ago
Can you explain how that is? Like with an example?
I’m not sure what you’re asking about. Explain what with an example?
Math is exactly like English. It’s a language
No it isn’t. It’s a tool for calculating things, with syntax rules. We even have rules around how to say it when speaking.
It’s an abstraction to describe something
And that something is the Laws of the Universe. 1+1=2, F=ma, etc.
Hell the word statement is used in math and English for a reason
You won’t find the word “statement” used in Maths textbooks. I’m guessing you’re referring to Expressions.
HereIAm@lemmy.world 3 weeks ago
100% with you. “Left to right” as far as I can tell only exists to make otherwise “unsolvable” problems a kind of official solution. I personally feel like it is a bodge, and I would rather the correct solution for such a problem to be undefined.
SmartmanApps@programming.dev 1 day ago
100% with you. “Left to right” as far as I can tell only exists to make otherwise “unsolvable” problems a kind of official solution
It’s not a rule, it’s a convention, and it exists so as to avoid making mistakes with signs, mistakes you made in almost every example you gave where you disobeyed left to right.
Robust_Mirror@aussie.zone 3 weeks ago
It’s so we don’t have to spam brackets everywhere
9+2-1+6-4+7-3+5=
Becomes
((((((9+2)-1)+6)-4)+7)-3)+5=
That’s just clutter for no good reason when we can just say if it doesn’t have parentheses it’s left to right. Having a default evaluation order makes sense and means we only need parentheses when we want to deviate from the norm.
SmartmanApps@programming.dev 1 day ago
It’s so we don’t have to spam brackets everywhere
No it isn’t. The order of operations rules were around for several centuries before we even started using Brackets in Maths.
((((((9+2)-1)+6)-4)+7)-3)+5
It was literally never written like that
we only need parentheses when we want to deviate from the norm
That has always been the case
barsoap@lemm.ee 3 weeks ago
It’s ambiguous which one of these is correct. Hence the best method we have for “correct” is left to right.
The solution accepted anywhere but in the US school system is “Bloody use parenthesis, then”, as well as “Why is there more than one division in this formula why didn’t you re-arrange everything to be less confusing” up to “50 Hertz, in base units, are 50s^-1^”.
SmartmanApps@programming.dev 1 day ago
The solution accepted anywhere but in the US school system range from “Bloody use parenthesis, then” over “Why is there more than one division in this formula why didn’t you re-arrange everything to be less confusing” to “50 Hertz, in base units, are 50s-1”.
No, the solution is learn the rules of Maths. You can find them in Maths textbooks.
so no actual mathematician, or other people using maths in earnest, use that kind of notation.
Yes we do, and it’s what we teach students to do.
HereIAm@lemmy.world 3 weeks ago
I fully agree that if it comes down to “left to right” the problem really needs to be rewritten to be more clear. But I’ve just shown why that “rule” is a common part of these meme problems because it is so weird and quite esoteric.
SmartmanApps@programming.dev 1 day ago
Nope! 6 × 4 ÷ 2 × 3 ÷ 9 =4 right to left is 6 ÷ 9 x 3 ÷ 2 × 4 =4. You disobeyed the rule of Left Associativity, and your answer is wrong
Also nope. Multiplication first is 6 x 4 x 3 ÷ 2 ÷ 9 =4
Still nope. 6 × 4 x 3 ÷ 2 ÷ 9 =4
Still nope. 6 × 4 x 3 ÷ 9 ÷ 2 =4
And finally still nope. 6 ÷ 9 ÷ 2 x 4 x 3 =4
Hint: note that I never once added any brackets. You did, hence your multiple wrong answers.
No it isn’t. Only 4 is correct, as I have just shown repeatedly.
It’s because students don’t make mistakes with signs if you don’t change the order. I just showed you can still get the correct answer with different orders, but you have to make sure you obey Left Associativity at every step.