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Why '5+5+5=15' is wrong under the Common Core
Business Insider ^ | October 25, 2015 | Jacob Shamsian

Posted on 10/25/2015 3:53:05 PM PDT by grundle

Here's a "repeated addition" Common Core problem that's taught in third grade in US schools:

Use the repeated-addition strategy to solve: 5x3

If you answer the question with "5+5+5=15,” you would be wrong.

The correct answer is "3+3+3+3+3.”

Mathematically, both are correct. But under Common Core, you're supposed to read "5x3" as "five groups of three." So "three groups of five" is wrong.

According to Common Core defenders, this method will be useful when students do more advanced math. This way of reading things, for instance, can be used when students learn matrices in multivariable calculus in high school.

But parents aren't happy about it.

(Excerpt) Read more at businessinsider.com ...


TOPICS: Education
KEYWORDS: addition; arth; commoncore; education; math; mathematics; repeatedaddition
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To: kjam22
You gotta wonder what idiot decided memorizing multiplication tables wasn’t the way to learn multiplication.

Those idiots are School of Education academics that think that rote memorization is bad for students. They simply do not understand how to teach.

21 posted on 10/25/2015 4:09:49 PM PDT by 17th Miss Regt
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To: 17th Miss Regt

They do not want anyone’s brain to function with facts. All things are relative in their universe.


22 posted on 10/25/2015 4:09:56 PM PDT by taterjay
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To: 17th Miss Regt

I’m a fan of deductive reasoning and applying common sense solutions to things. But not to 5x3.


23 posted on 10/25/2015 4:12:45 PM PDT by kjam22
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To: grundle

I Thank God I went to school in the 1940’s


24 posted on 10/25/2015 4:13:01 PM PDT by Fiddlstix (Warning! This Is A Subliminal Tagline! Read it at your own risk!(Presented by TagLines R US))
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To: 17th Miss Regt

.
How can you get “single variable “calculus?

The differential of one variable with respect to another, the most basic concept of the calculus, demands at least two variables.

Do you have the slightest idea what the calculus is?

One wonders....
.


25 posted on 10/25/2015 4:13:20 PM PDT by editor-surveyor (Freepers: Not as smart as I'd hoped they'd be)
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To: Svartalfiar
Hmm.. Under the commutative law, 5x3 = 3x5. So it's kinda an extra step 'show your work', but it's not wrong. Does common core not teach commutative, transitive, associative properties, etc?

They are making a very pedantic distinction without a real difference here. And you can bet they did not mention commutativity of real numbers. This is the intellectual equivalence of creeping legalism being injected into math.

26 posted on 10/25/2015 4:15:13 PM PDT by 17th Miss Regt
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To: grundle

I have a BS in Mathematics from 1977. Went into computer programming and now I don’t remember much of the higher level math. But I do know my times tables...


27 posted on 10/25/2015 4:15:15 PM PDT by laker_dad
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To: W.
The 'teachers' seem to be trying to make their students stupider.

It's not the teachers. Most of them HATE this crap.

And I say that as a long-time high school teacher. Back in the old days (before, say, 2000), our district would pilot any proposed new methods. A couple of teachers would volunteer to teach the material, then report back to the rest of us.

Those teachers were very much encouraged to modify - and even discard - things that didn't make sense, or weren't working.

Today, we are all given a course syllabus. Even the slightest modification of the syllabus is not allowed.

28 posted on 10/25/2015 4:16:23 PM PDT by Leaning Right (Why am I holding this lantern? I am looking for the next Reagan.)
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To: grundle

Common Core isn’tt about teaching the students knowledge. Its about teaching them how to think the way they are told to think by a higher authority without question. It is a method of programming minds to follow orders. In short, its brainwashing.


29 posted on 10/25/2015 4:16:34 PM PDT by jsanders2001
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To: 17th Miss Regt

The problem is that the Common Core idiots don’t reallize that children do NOT think abstractly.

That doesn’t happen until teen age years.

Children not yet in puberty are concrete thinkers.


30 posted on 10/25/2015 4:16:59 PM PDT by metmom (...fixing our eyes on Jesus, the Author and Perfecter of our faith...)
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To: Paladin2
5 x 3 = 3 x 5

Yep. And if "they" want an advanced sounding excuse, give 'em "multiplication is commutative over real numbers." Then say something about minimization of computational complexity.

31 posted on 10/25/2015 4:20:38 PM PDT by Pearls Before Swine
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To: grundle
But...but...did they ask the chillen how they feel about the numbers?
32 posted on 10/25/2015 4:21:19 PM PDT by PROCON (A proud CRUZader.)
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To: W.

Same here. Even my hardcore “stick over the head” Catholic nun teachers in HS would revolt if they taught this way.


33 posted on 10/25/2015 4:21:36 PM PDT by max americana (fired every liberal in our company at every election cycle..and laughed at their faces (true story))
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To: editor-surveyor

I refer to calculus of a single variable x. Standard Newton-Leibnitz developed calculus of a single real variable. In so far as your statement, “The differential of one variable with respect to another, the most basic concept of the calculus, demands at least two variables.”, that makes no sense. In single variable calculus, values of y are generally determined by the value of an input variable x. Thus y is not a variable itself but rather a function of a variable x.


34 posted on 10/25/2015 4:21:41 PM PDT by 17th Miss Regt
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To: 17th Miss Regt
Those idiots are School of Education academics that think that rote memorization is bad for students.

That's exactly right! Any teacher will tell you that rote memorization is really the first step towards true understanding.

But the School of Education academics need to "publish or perish". So they are always generating garbage, garbage that gets latched on by "progressive" school superintendents.

The garbage doesn't work, and then the teachers get blamed.

University Schools of Education should be abolished. If you want to be, say, a math teacher, you should have to do it through the university math department.

35 posted on 10/25/2015 4:23:43 PM PDT by Leaning Right (Why am I holding this lantern? I am looking for the next Reagan.)
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To: grundle
Mathematically, both are correct. But under Common Core, you're supposed to read "5x3" as "five groups of three." So "three groups of five" is wrong.


36 posted on 10/25/2015 4:24:35 PM PDT by Greetings_Puny_Humans (I mostly come out at night... mostly.)
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To: metmom

That is absolutely correct. When students begin to be able to think in abstract terms varies by child but it has a profound effect on their ability to learn mathematics. Some cannot do it until they are 15 or 16, others can do it when they are 12 or 13. Seldom does the ability develop before then.


37 posted on 10/25/2015 4:24:58 PM PDT by 17th Miss Regt
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To: PROCON

And then a smart aleck kid comes back with, “I have many conflicting feelings about this number. It’s very complex!”


38 posted on 10/25/2015 4:26:44 PM PDT by 17th Miss Regt
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To: grundle

I’d like to see this sort of reasoning being applied to a Boolean Logic question, or a Euclidean Geometry question.


39 posted on 10/25/2015 4:29:36 PM PDT by Terry L Smith
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To: tet68

“Honestly, I used to think I received a poor education
in the 1950s, now I bless it.”

Well, back in the 50’s they had infinitely quantities to spend, where today they always have to fight budget shortfalls


40 posted on 10/25/2015 4:31:28 PM PDT by dsrtsage (One half of all people have below average IQ. In the US the number is 54%)
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