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Dumbfounded. 
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Maybe the one invented was frightened, that the youngster will understand core math - so he came up with this mess...
By the way - there is a place where actually using it to teach math?
I'm not questioning your powers of observation; I'm merely remarking upon the paradox of asking a masked man who he is. (V)
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Here in Arizona and many other places. It has actually become a political campaign issue.
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Since when politicians new about math anything? Poor kids...
I'm not questioning your powers of observation; I'm merely remarking upon the paradox of asking a masked man who he is. (V)
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Here's a post about the merits of it[^], or at least why it's not really that bad.
tl;dr version: it's basically the way everyone figures out change.
Or in other words, it's preparing them for their likely future life as a McD clerk. 
TTFN - Kent
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Kent Sharkey wrote: it's basically the way everyone figures out change
Except for that it isn't.
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I dunno, if I had to figure out 1000-995, I don't think I'd be carrying any 9s.
I'm not saying it's a good system, I just don't think it's as crazy as some people are making it out to be.
TTFN - Kent
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What is 92-27? To do it in your head I believe most people will round to something familiar and go from there.
There are only 10 types of people in the world, those who understand binary and those who don't.
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Excuse me, but RUBBISH...I was good with math when was young (I'm still not that bad) and I do understand numbers - it's not the way I ever done things...
I'm not questioning your powers of observation; I'm merely remarking upon the paradox of asking a masked man who he is. (V)
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Kornfeld Eliyahu Peter wrote: it's not the way I ever done things
I agree it's weird to anyone with more maths ability than a gnat or gnu, but how often has something like this happened:
Green Grocer: That'll be £7.93 please.
Me: [Hands over £10] There you go, thanks.
Green Grocer: [Hands over 7p] - eight quid
[Hands over £1] - nine quid.
[Hands over £1] - Tenner!
That's the basis of the insano-method
Alberto Brandolini: The amount of energy necessary to refute bullshit is an order of magnitude bigger than to produce it.
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Aye. It works well for that. Not for maths in general, though!
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Kent Sharkey wrote: Here's a post about the merits of it[^], or at least why it's not really that bad.
I see how using the base as a reference point is a good thing for mental math; I do that already. But they way they implemented it is just retarded.
In the case of 325 - 38, why not just do something more like 325 - 40 + 2 to get the answer? Or hell even (325 - 25) - 40 + 25 + 2? You get the benefit of it being easier mentally without all the extra crappy steps.
Jeremy Falcon
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Yeah, that would work for me as well (although that first solution looks to me pretty much common core, just reversed).
I suspect this all grew out of some PhD in Education writing their thesis on, "Why Johnny can't carry a 9". Then (as is often the case), they choose the worst solution.
TTFN - Kent
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It seems to me that those of us who are really good at mental arithmetic have always solved problems differently depending on context. The reality is that we rarely use long subtraction, but use all manner of shortcuts. It's a little like programming: We take a first look at the problem; determine a method, based on experience; we implement. As we learn new tricks and put them into practice we add them to our list of methods, sometimes replacing old ones (I still, rarely, use DOS batch file coding!)
The trouble with teaching maths using that approach is that kids need to start learning one way. If an experienced maths teacher says that they found it easier to teach this way, I'd take his word for it. Bad explanations and bad examples only serve to reinforce our prejudices ("That's not how I was taught to do it!") As programmers, I would hope that we'd be open to consider new techniques?
I do think that there is merit in learning the "granny" method too, because sometimes the "simpler" tricks break down and the problem is too complex to solve with a hack!
Life is like a s**t sandwich; the more bread you have, the less s**t you eat.
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So here's an other idea. Teach the reasonable algorithm, and then actually explain it. Wow! Shocking, I know. I bet no one thought of that.
It is after all not that hard to see why it works and what you're doing. If students didn't get it, it's because no one explained it.
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The problem with this system is that it works for subtraction and it is very easy, probably easier then the traditional carry method we all learnt. But that is it. It ONLY works for subtraction. The multiplication method is different, division is different.
In other words common core ignores what is common.
A + B = C --> C - A = B & C - B = A
A x B = C --> C / A = B & C / B = A
And as soon as you move into negatives, algebra and real geometry it's useless.
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Presenting a reasonable, rational argument? Do you belong on the Internet? 
Yeah, I was thinking of it in isolation (where I still think as a first method it makes more sense than the traditional method). However, as you point out, other than in isolation it doesn't make sense. Plus - as others have pointed out - this is being taught to older kids who supposedly have already integrated the older method, confusing them. Definitely makes less sense to me now.
Fortunately, no kids in the system.
TTFN - Kent
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Kent Sharkey wrote: Or in other words, it's preparing them for their likely future life as a McD clerk.
This is the real problem - education not for education's sake, but to become a good little worker/consumer in later life.
Alberto Brandolini: The amount of energy necessary to refute bullshit is an order of magnitude bigger than to produce it.
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My kid was taught lattice multiplication in the common core ciriculum, a technique some 700 years old. It required the abiliy to draw neatly, something my 3rd/4th grader could not do (neither can I) and he got the wrong answer 8-9 times out of 10,because of this inability to draw neatly. Doing long multiplication the tradional way he got the right answer 8-9 times out of ten. When I queried his teacher about this rediculous method, she replied "Gee, I don't really understand it either, but I'm required to do this now.".  
"the debugger doesn't tell me anything because this code compiles just fine" - random QA comment
"Facebook is where you tell lies to your friends. Twitter is where you tell the truth to strangers." - chriselst
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My son's just started 6th grade.
We are constantly emailing his math teacher with WTF's.
He constantly writes back, "Yes, this new way is confusing, but..."
If it's not broken, fix it until it is
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They're teaching this in grade six?  Doesn't that mean that they're now trying to override the way they already learned? Then that definitely doesn't make sense.
TTFN - Kent
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No one said it made sense
If it's not broken, fix it until it is
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Kent Sharkey wrote: Doesn't that mean that they're now trying to override the way they already learned?
Yes. One of the biggest problems in the US is the constantly changing curriculum requirements. This means that what you taught in 6th grade might be re-taught in 7th, or that the new 7th grader is expected to have been taught something different in 6th grade as a the basis for what they are going to learn in 7th grade. My son, who was getting a math-teaching degree at SUNY New Paltz, explains that the curriculum can literally change 2 or 2 times in a school year.
Furthermore, because of "No child left behind" and other rubbish (and we can't blame Bush, the tenets of NCLB goes back to the 50's, if not earlier actually) the teacher MUST teach to the curriculum, paced at whatever some bureaucrat decided, because the teacher is graded on how the kids score, so teaching does nothing more than attempt to teach how to pass a test.
Every teacher I've talked with hates this system, but what do you expect from a curriculum that was decided in a national conference where all the decision makers were business people, and only one, yes one, I kid you not, teacher was invited to said conference.
This country is so FUBAR. Sadly, when I talked to a couple college kids from France, they say their educational system is even worse!!!
Marc
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Marc Clifton wrote: Yes. One of the biggest problems in the US is the constantly changing curriculum requirements. This means that what you taught in 6th grade might be re-taught in 7th
Marc Clifton wrote: My son, who was getting a math-teaching degree at SUNY New Paltz, explains that the curriculum can literally change 2 or 2 times in a school year.
That's exactly the kind of stuff that the common core is supposed to get rid of.
A lot of the districts get locked into proprietary systems for curricula and tracking progress, which puts a lot of limits on teachers. The foundation I work for is working on getting all states to adopt a common data standard for student level data, so that they can be freed from vendor lock-in along with fixing many other common woes.
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Andy Brummer wrote: The foundation I work for is working on getting all states to adopt a common data standard for student level data,
How can you do that with the amount of cultural and economic diversity that is found, not just among different states, but among schools within a state?
Marc
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