this post was submitted on 12 Dec 2023
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6÷2(1+2) (programming.dev)
submitted 1 year ago* (last edited 1 year ago) by [email protected] to c/[email protected]
 

https://zeta.one/viral-math/

I wrote a (very long) blog post about those viral math problems and am looking for feedback, especially from people who are not convinced that the problem is ambiguous.

It's about a 30min read so thank you in advance if you really take the time to read it, but I think it's worth it if you joined such discussions in the past, but I'm probably biased because I wrote it :)

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[–] [email protected] -4 points 1 year ago (2 children)

No, those companies aren't wrong, but they're not entirely right either. The answer to "6 ÷ 2(1+2)" is 1 on those calculators because that is a badly written equation and you(not literally you, to be clear) should feel bad for writing it, and the calculators can't handle it with their rigid hardcoded logic. The ones that do give the correct answer of 9 on that equation will get other equations wrong that it shouldn't be, again because the logic is hardcoded.

That doesn't change the fact that that equation worked out on paper is absolutely 9 based on modern rules of math. Calculate the parentheses first, you then have 6 ÷ 2(3). We could solve from here, but to make the point extra clear I'm going to actually expand this out to explicit multiplication. "2(3)" is the same as "2 x 3", so we can rewrite the equation as "6 ÷ 2 x 3". All operators now inarguably have equal precedence, which means the only factor left in which order to do the operations is left to right, and thus division first. The answer can only be 9.

[–] [email protected] 9 points 1 year ago (2 children)

If you'd ever taken any advanced math, you'd see that the answer is 1 all day. The implicit multiplication is done before the division because anyone taking advanced math would see 2(1+2) as a term that must be resolved first. The answer still lies in the ambiguity of the way the problem is written though. If the author used fractions instead of that stupid division symbol, there would be no ambiguity. It's either 6/2 x 3 = 9 or [6/(2x3)] = 1. Comment formatting aside, if someone put 6 in the numerator, and then did or did NOT put all the rest in the denominator underneath a horizontal bar, it would be obvious.

TL;DR It's still a formatting issue, but 9 is definitely not the clear and only answer.

[–] [email protected] 1 points 9 months ago (1 children)

If you’d ever taken any advanced math, you’d see that the answer is 1 all day

Don't need to do advanced Maths - every rule you need to know for this problem is taught in Year 7.

[–] [email protected] 1 points 9 months ago (1 children)

"Always remember to solve using PEMDAS once you've used the distributive property!" Link%20and%20subtraction%20(S).)

(emphasis mine)

[–] [email protected] 0 points 9 months ago (1 children)

And...? Not sure what your point is, but the link is VERY badly worded...

  1. The Distributive Law and The Distributive Property aren't the same thing - he's applying The Distributive Law, but mistakenly calling it The Distributive Property (a lot of people make that mistake). The latter is merely a property in Maths (like the commutative property, the associative property, etc.), the former an actual rule of Maths The Distributive Law
  2. Applying the Distributive Law - i.e. expanding brackets/parentheses - is part of solving brackets. i.e. the first step in BEDMAS/PEMDAS. There's no "once you've used", you've already started!
  3. As I already said, this is taught in Year 7, so I'm not sure what your point is?
[–] [email protected] 0 points 9 months ago (1 children)

That you're still wrong? As I said, the true answer is that the problem is written poorly due to the obelus and thus is open to interpretation. You're entitled to your own interpretation since it's written poorly, I just find it pretty obviously less logical than multiplying using the distributive property first to resolve the term with the parentheses fully as you would in any advanced math.

Also, distributive law and distributive property are the same thing per Khan academy "The distributive property is sometimes called the distributive law of multiplication and division."

Wait till you hear that "i before e except after c" wasn't true either. It's wild that you think 7th grade math overrules grad school math though lol.

[–] [email protected] 1 points 9 months ago

That you’re still wrong?

About? You haven't pointed out anything that's wrong.

the problem is written poorly due to the obelus and thus is open to interpretation

Oh, you're one of those people. Good, maybe we can finally get an answer then (this was also talked about in the blog). What other interpretation of an obelus is possible other than division? People keep saying it's ambiguous, but no-one has ever said why (other than some stuff that makes no sense in the context, as explained in the blog)

The distributive property is sometimes called the distributive law of multiplication and division

Yes, and sometimes people call Koalas "Koala bears", but that doesn't mean they're bears. Now bearing that in mind, read again what Khan said - the page which is called "Distributive property explained", not "Distributive Law explained".

Wait till you hear that “i before e except after c” wasn’t true either

Wait till you hear that's not a rule of Maths.

It’s wild that you think 7th grade math overrules grad school math though

Umm, never said anything of the kind...

[–] [email protected] 0 points 10 months ago (1 children)

The answer still lies in the ambiguity of the way the problem is written though

But it's not ambiguous, as per the reason you already gave.

If the author used fractions instead of that stupid division symbol

If you use fractions then the whole thing is a single term, if you use division it's 2 terms.

9 is definitely not the clear and only answer

1 is definitely the only answer.

[–] [email protected] 0 points 10 months ago (1 children)
[–] [email protected] 0 points 10 months ago

"The obelus is treated differently,” Church said. "It could mean ratios, division or numerator and denominator, and these all tweak the meaning of the symbol.”

This is the only symbols I've ever seen used (but feel free to provide a reference if you know of any where it isn't - the article hasn't provided any references)...

Ratio is only ever colon.

Division is obelus (textbooks/computers) or slash (computers, though if it's text you can use a Unicode obelus).

Fraction is fraction bar (textbooks) or obelus/slash inside brackets (computers). i.e. (a/b).

[–] [email protected] 0 points 10 months ago

those calculators because that is a badly written equation

It's not badly written, and the reason Texas Instruments gets it wrong is right there in their manual (disobeys The Distributive Law).

modern rules of math

The order of operations rules haven't changed in at least 100 years, and more likely at least 400 years. Don't listen to Youtubers who can't cite a single Maths textbook.

“2(3)” is the same as “2 x 3”

No, it's the same as (2x3), as per The Distributive Law and Terms.