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I cringe at those basic math question posted on the web.

What's annoying about those math questions is often it's a trick to see if you caught that lone minus sign among the various pluses.
5+5+4+4+5+5+55+5=?
And then this is labeled an IQ test. Wow.

1 hour ago, magicalclick wrote
@evildictaitor: I dislike those things. People start to say add before subtract because those things. I am like, dude, addition and subtraction has the same order.
But + and  commute, so it doesn't matter :/

3 hours ago, cbae wrote
@Blue Ink: Kind people come over for good spaghetti. Anybody remember that one?
I like xkcd's new proposal better.

103+2=5 if you add before subtract, but should be 9.
(Example stolen from Wikipedia)

And remember, 25 divided by 5 is 14 ...

17 hours ago, Sven Groot wrote
Lots of people just don't remember the operator order, which is hardly surprising since it's not something most people actually need very often.
Yea but everyone learns it in school, and its pretty intuitive, meaning its not hard to forget. So I still don't get it.

9 hours ago, magicalclick wrote
@evildictaitor: I dislike those things. People start to say add before subtract because those things. I am like, dude, addition and subtraction has the same order.
When operators have the same precedence we associate, i.e., left to right association in case of + and  operators

It's not necessarily about getting it right. When you get something wrong you inevitably learn why. Then, you acquire new knowledge that stays with you.
All of us would get each of the examples in this thread wrong at some point in time > the points in time when we didn't know anything about order precedence of mathematical operations.
Here's to ignorance and the pursuit of knowledge. You can't have one without the other.C

1 hour ago, Charles wrote
It's not necessarily about getting it right. When you get something wrong you inevitably learn why. Then, you acquire new knowledge that stays with you.
All of us would get each of the examples in this thread wrong at some point in time > the points in time when we didn't know anything about order precedence of mathematical operations.
Here's to ignorance and the pursuit of knowledge. You can't have one without the other.C
Well Put!
Another way to think about it is terms of a state machine.
We can get from a state of 1."Not Knowing" to a state of 2."Knowing" (here state of knowing may not be absolute) with multiple iterations.
And the transition from state 1 to 2 can be learning/experience/observation/accidental.

2 hours ago, brian.shapiro wrote
*snip*
Yea but everyone learns it in school, and its pretty intuitive, meaning its not hard to forget. So I still don't get it.
Yeah, and I learned in school which French verbs should be conjugated with être rather than avez, and I'm sure that to people who actually use French regularly that's perfectly intuitive and easy to remember. Yet I never use this in my daily life, so I've completely forgotten them all.
And I can't think of any instance outside of my work where knowing about operator precedence was actually necessary.

Thanks for the good laugh... my teammates just looked at me as if I had gone crazy.

3 hours ago, Charles wrote
It's not necessarily about getting it right. When you get something wrong you inevitably learn why. Then, you acquire new knowledge that stays with you.
All of us would get each of the examples in this thread wrong at some point in time > the points in time when we didn't know anything about order precedence of mathematical operations.
Here's to ignorance and the pursuit of knowledge. You can't have one without the other.C
I don't have problem for people getting it wrong, but have problem where the teachers teach it without explaining the fundamential reason of doing so.
Once you know the reason, even if you forgot the order, you can deduce it correctly yourself. It's all related to converting goods to their monetary value. "M"oney is the basis of ancient "M"athematics.

@Charles: I know we all make mistakes. Have you actual read their lengthy explanation on why their wrong answer is correct? After they already read so many people telling them the right answer already? And I really do not see how one can forgot or confused about it, because with my terrible memory, who I still cannot remember my parents bday except my bro's 123, I find it very easy to remember. Actually you only need to remember one thing only, + has () around it. And that's it. Everything else really has no brainer, like tiny power number attached to a large number, which is very obvious the tiny number belongs to the attaching number.

I am disappointed that the term "Calculus" was never mentioned to me all throughout my high school years. I took Physics 12, Math 12 H, Chem 12, and equations were just thrown at us to memorize and learn to manipulate algebraically, but no mention of where or how such equations / formulas came about. No mention of deferential equations or calculus. I do not understand why.
I graduated, with honors, in 1978. I learned Calculus, or perhaps I should say studied it a couple of years later when I went to university. However, it wasn't until about 10 years ago that I began studying Calculus, and studied it intensely, daily, for 6 years or so (with a few excursions between cover to cover studies of my 1,000 page calculus book, to read a 1,000 page physics book and a strength of materials book)
This calculus study was sparked by my need to understand the topic of "The Finite Element Method". After studying said topic for 2 months, still nothing of what I studied made any sense. The appendix of vectors and matrixes, a fundamental topic for studying FEM, was the last straw that "forced" me to finally study the calculus. It has changed my world.
Question to C9ers: Is calculus mentioned in high school today?

@Proton2: Calculus is definitely mentioned in high school today. I graduated in 2003 from High School and there were a lot of seniors taking Calculus, myself included. It's not for every student, of course, and there are a lot of students who aren't ready for it, but it's there if you're able. And even though I went to several high schools, the one I graduated from only had a graduating class of 100ish, so it's not just the "big" high schools that offer it.

@Proton2: that's my experience back in Taiwan. All equations with very little explanations. Then I come to US relearn everything again, and it is so much easier to understand because they took time to explain it. They even explain the previous class material just in case we forgot. Well, maybe because I took it the second time in US, it is a lot easier for me to understand as well. Something I always liked about US math for lagging 4 years. I have something to compete off the plane.

10 hours ago, cheong wrote
*snip*
I don't have problem for people getting it wrong, but have problem where the teachers teach it without explaining the fundamential reason of doing so.
Once you know the reason, even if you forgot the order, you can deduce it correctly yourself. It's all related to converting goods to their monetary value. "M"oney is the basis of ancient "M"athematics.
The problem is that operator precedence is largely a convention; there's no real reason why 3 + 3 * 4 = 15 and not 24; it's just that we decided it has to be that way.
That's what makes it hard to teach: you can paraphrase it all you want, but the answer is essentially "just because" and that never flies too well with kids.

1 minute ago, Blue Ink wrote
*snip*
The problem is that operator precedence is largely a convention; there's no real reason why 3 + 3 * 4 = 15 and not 24; it's just that we decided it has to be that way.
That's what makes it hard to teach: you can paraphrase it all you want, but the answer is essentially "just because" and that never flies too well with kids.
Sure there's a reason. If the operators applied based on order in the equation, then the operations couldn't be freely associated with each other and always would have to be put in place in a certain order. For example, lets say you had an equation x × 2 = y × 3. You want to be able to rewrite the equation as x × 2  y × 3 = 0 and still have it mean the same thing without putting in parentheses. If it was based on the order in the equation you couldn't do that very well. Stacking operations isn't very intuitive for people, only useful for calculators that can only enter one operation at a time. And if you had addition/subtraction taking precedence before multiplication/division you would have something that was intuitively strange, too.
Its not absolutely necessary, of course, but there's a reason behind it; its not arbitrary that standard order of operations works like that.
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