Stupid 'new' math question - am I right or wrong here?

[dullard]

I believe the order of operations rule that applies here is that when you have operations of the same rank, you move from left to right. Using that rule the only correct english interpretation of 5 x 3 is five three times.

Except it is (five times) of (three). Not (five) done (three times). Notice how you moved the multiplication symbol when reading. You shifted (5) x (3) to (5) (3 x).

 

[crashtech]

Using English (probably other languages as well) to work a math problem confuses the hell out of people. It's difficult for many to accept that words do not have the same rigid meaning as mathematical symbols.

Yet countless word problems can be presented that each have only one correct answer. So words, properly used, can be precise.

 

[DigDog]

Multiplication is commutative. You're both right.

he is correct only if Humpy = 0. if Humpy = 1 then he is not correct. do not prove the problem.

this reminds me i still haven't blocked that guy. need to do.

 

[Ruptga]

Yet countless word problems can be presented that each have only one correct answer. So words, properly used, can be precise.

That's true only when their precise meaning is known. A person fluent in the language that is unfamiliar with the idiosyncrasies of whatever field a word problem relates to can and often does misinterpret the problem. This is why high level math uses symbols from formal logic instead of of plain word problems, it removes the ambiguity of natural language by not using natural language.

 

[tynopik]

(dupe)

 

[tynopik]

You are answering the wrong question. It wasn't about how to get the correct answer, it was about the text book's english interpretation of the problem which, as described, is wrong.

there is nothing wrong with the textbook's interpretation

I believe the order of operations rule that applies here is that when you have operations of the same rank, you move from left to right. Using that rule the only correct english interpretation of 5 x 3 is five three times. In other words 5 + 5 + 5.

no

order of operations only applies to multiple operations

in 5*3 there is only one operation so it's nonsensical to apply those rules

also, even if you did read it left to right, it is plainly ambiguous in English

there's nothing that says '5 items 3 times' is clearly better than '5 groups of 3'

both are equally valid interpretations

in fact, my preference would be the latter

 

[crashtech]

That's true only when their precise meaning is known. A person fluent in the language that is unfamiliar with the idiosyncrasies of whatever field a word problem relates to can and often does misinterpret the problem. This is why high level math uses symbols from formal logic instead of of plain word problems, it removes the ambiguity of natural language by not using natural language.

I agree that symbols are the preferred method of expressing mathematical problems, but one's failure to properly interpret any given word problem is not indicative of the written words' ability to be precise.

 

[Humpy]

he is correct only if Humpy = 0. if Humpy = 1 then he is not correct. do not prove the problem.

this reminds me i still haven't blocked that guy. need to do.

WTF? Hopefully you've been drinking again.

That's true only when their precise meaning is known. A person fluent in the language that is unfamiliar with the idiosyncrasies of whatever field a word problem relates to can and often does misinterpret the problem. This is why high level math uses symbols from formal logic instead of of plain word problems, it removes the ambiguity of natural language by not using natural language.

Exactly.



Just LOL at adults stubbornly flailing around trying to explain 5x3.

 

[Red Squirrel]

Think it depends on what's easier for the person. Personally I find groups of 5 are easier to add than groups of 3, so I would tend to group it in 3 groups of 5, and I automatically know it's 15, but 5 groups of 3 takes a bit more "brain power" to calculate as it's not as round of a number. So say it was like 5 * 7, I would use 7 groups of 5 vs 5 groups of 7.

 

[zinfamous]

Yet countless word problems can be presented that each have only one correct answer. So words, properly used, can be precise.

That's true only when their precise meaning is known. A person fluent in the language that is unfamiliar with the idiosyncrasies of whatever field a word problem relates to can and often does misinterpret the problem. This is why high level math uses symbols from formal logic instead of of plain word problems, it removes the ambiguity of natural language by not using natural language.

Guys, you missed this little gem recently. Humpy still contends that his embarrassing fail was not embarrassing fail.

http://forums.anandtech.com/showthread.php?t=2473367&highlight=math+problem

The fun starts at post 35 and just gets better.

 

[DrPizza]

So our son is in 1st grade and they are learning multiplication. The way they are teaching it is really bothering me. Either they are retarded or my whole life has been a lie. ATOT decides.

Ok so the problem is:

5 x 3

The way the textbook describes this is "5 groups of three" so 3 + 3 + 3 + 3 + 3

As opposed to the way I read the problem which is "3 groups of five" or 5 + 5 + 5

Yes, they should just teach multiplication tables and automatically know the answer, but that's a different rant.

The textbook interpretation of 5 x 3 doesn't make any sense to me and seems contrary to the English language.

So ATOT - am I right or is the school right?

So, when you got to Algebra, you must have been confused, since now you had to figure out that it was easier to deal with 5x as 5 unknowns, rather than an unknown number of 5's.

It's really nice when material is kept consistent - better understanding in the long run.

FAIL.

 

[Humpy]

Guys, you missed this little gem recently. Humpy still contends that his embarrassing fail was not embarrassing fail.

http://forums.anandtech.com/showthread.php?t=2473367&highlight=math+problem

The fun starts at post 35 and just gets better.

:biggrin: That thread really got to some of you.

 

[Humpy]

So, when you got to Algebra, you must have been confused, since now you had to figure out that it was easier to deal with 5x as 5 unknowns, rather than an unknown number of 5's.

It's really nice when material is kept consistent - better understanding in the long run.

FAIL.

Is this "groups of" shit really how they teach kids multiplication these days?

What happened to:

Is it 5 columns of 3 or 3 rows of 5?

 

[zinfamous]

:biggrin: That thread really got to some of you.

I was just trying to inform your comment to those not in the know.

 

[DrPizza]

Is this "groups of" shit really how they teach kids multiplication these days?

What happened to:

Is it 5 columns of 3 or 3 rows of 5?

Not sure if you understand it, but multiplication is a short cut for repeated addition. 3+3+3+3+3 = 5(3)
x+x+x+x+x = 5x
And, in your little picture, there are 5 columns of 3. Yes, multiplication is commutative - there are 3 rows of 5, but in teaching what 5x3 is, doesn't it make a hell of a lot more sense to look at the big picture and realize that in a few years, the kids are going to have to understand what 5x means?

 

[Humpy]

Not sure if you understand it, but multiplication is a short cut for repeated addition. 3+3+3+3+3 = 5(3)
x+x+x+x+x = 5x

Ah, a snarky reply! 4/10 attempt, but I still like it.

That's what's nice about the visualization of units, it demonstrates the relation of addition and multiplication in one simple picture, as well as other basic concepts like calculating area and spatial logic by rearranging and dividing the units.

I was actually wondering if it is still taught that way. Maybe someone else knows.

And, in your little picture, there are 5 columns of 3. Yes, multiplication is commutative - there are 3 rows of 5, but in teaching what 5x3 is, doesn't it make a hell of a lot more sense to look at the big picture and realize that in a few years, the kids are going to have to understand what 5x means?

I guess to me the big picture is bigger than understanding someone's idea of what 5x "means".

 

[John Connor]

Sounds like common core bull shit to me, OP.

 

[Humpy]

Sounds like common core bull shit to me, OP.

The OP is a years old internet curiosity originating, maybe from the same textbook, when a homework answer of 5+5+5 was supposedly marked wrong because 3+3+3+3+3 was what was taught as the equivalent of 5x3.

With educated adult's arguing that there is actually a difference it's no wonder millennials grew up to be like "fuck it, just hand me the answer so we can move on".

 

[CraKaJaX]

because some facebook post told you so?

Actually I saw it on my Twitter feed. D:

 

[Tequila]

I'm not bitter, I'm trying to actually make the world a bit better, one person at a time.

Common core isn't the problem and isn't a disaster like you said. The problem is poor teaching, over testing, and lack of understanding from everyone involved.

Lets attack the real problems. I'd rather go after poor teaching than just let blanket statements like the ones from you and SamQuint go by. Kneejerk blanket statements bashing Common Core don't help anyone and aren't constructive. I wouldn't be surprised if even more people chime in complaining about Common Core when that has nothing to do with the problem.

Let teach that both multiplication orders (relating to the OP) are correct and both are useful. Then lets teach them how to create either order from actual problems, why one order may be more useful in some cases than others, and even more importantly how to use the results.

If poor teaching is the problem then how is Common Core going to solve it when it seems to complicate things even more? I've seem other examples of CC and they border on the ridiculous. This one for example https://www.google.com/search?q=com...=w_5OV7qNFoKAjwPFrLvgAQ#imgrc=YFp29tCcoXdmRM:

I'd want to kill myself if I had to solve it using CC.

This is even worse https://www.google.com/search?q=com...=w_5OV7qNFoKAjwPFrLvgAQ#imgrc=BNM-iq5uY8v2_M:. Are you freakin kidding me?

 

[Humpy]

If poor teaching is the problem then how is Common Core going to solve it when it seems to complicate things even more? I've seem other examples of CC and they border on the ridiculous. This one for example https://www.google.com/search?q=com...=w_5OV7qNFoKAjwPFrLvgAQ#imgrc=YFp29tCcoXdmRM:

I'd want to kill myself if I had to solve it using CC.

This is even worse https://www.google.com/search?q=com...=w_5OV7qNFoKAjwPFrLvgAQ#imgrc=BNM-iq5uY8v2_M:. Are you freakin kidding me?

It's nice how the common core easily exposes the simpletons. So there's that.

20 x 1 = 1+1+1+1+1+1+1+1+1+1+1+1+1+1+1+1+1+1+1+1

See, it's 20 groups of 1! It's a shortcut! You'll miss the big picture if you think of it as 1 group of 20. Derp.

 

[Ruptga]

Common Core: the new bogeyman from the people that brought us "death panels".

 

[Ken g6]

I have an idea. Let's teach everyone postfix notation! It gets rid of parentheses, plus it reads this problem unambiguously.

5 x 3 in postfix is "5 3 x", or "five three times".

 

[sactoking]

I love when people blame the "common core" boogeyman without understanding what it is. It is a set of educational standards dictating the educational concepts that must be taught, it is not the specific curriculum that is used in teaching those concepts. There are many different curriculae approved to meet valid standards and they all teach those standards differently. If you take umbrage with how 5x3 or some other concept is being taught don't blame common core, blame the curriculum peddler.

Beyond that this thread seems to be a whole bunch of "it was better when I was a kid" moaning. How many of you learned to add multiple numbers by aligning them vertically then adding from right to left while carrying values in excess of 9? Most experts will tell you that it's much faster to add left to right instead.

 

[pcgeek11]

I was always taught that 5 x 3 is equal to five groups of three.


3 + 3 + 3 + 3 + 3 = 5 x 3

5 is the multiplier X 3 is the multiplicand = 15 is the product

3
x5

5 + 5 + 5 = 3 x 5

3 is the multiplier X 5 is the multiplicand = 15 is the product

5
x3