CommieCore Math

[MeshugeMikey]

to quote dontreathis::

“I can’t see a rational purpose for these contortions”

reinventing the wheel is contraindicated...and doubly so in childhood!

[moose07]

Fill each square in using the simple times table.
Eg 7*3= 21 First square.
Add up the diagonals ,placing results at bottom.
(6, 1+5+2= 8, 2+2+3+6= 13 , 1+6+1+ carry 1=9 )= 9386
Carry bits are added to next column, like normal addition.

The answer appears along the bottom like magic.

[scrabblehack]

I suppose they teach the kids to count by fives. So, 12 plus how many is the next higher multiple of 5?
12 + 3 = 15.
Now, add multiples of 5 until you get to a multiple of 10.
15 + 5 = 20.
Now that you have a multiple of 10, keep adding tens until you get within 10 of your goal.
20 + 10 = 30.
Now, how many to your goal? 2.
30 + 2 = 32.
Now, add 3 + 5 + 10 + 2 = 20.

It seems a convoluted way of subtracting 12 from 32, but yes it is correct.

[so_real]

The larger the numbers grow, the less sustainable this ridiculous method becomes. Try subtracting a seven digit number from a nine digit number this way. Then flip it and subtract the larger from the smaller. The poor child's head will explode.

[prof.h.mandingo]

Your example makes more sense than the crap they used in the common core math example.
What you did was count on your fingers and add 5 toes. It’s a good think you didn’t have to count to 21 unless you are a male. 22 about taps us out. That of course if unfair to our female students.
I have seen some of this and it is indeed scary.

[Gene Eric]

Here's an explanation:

Given:  32-12=20

Notice the first term in the 4 line progression is the value (12) subtracted from the result(32) in the last line:
12..=..
 .. =..
 .. =32

In each line of the progression, notice how the result is used as the first term in the next line:

12+3=15
15+...

The lines are essentially chained together where the incremental values to the right of the + represent the total increase from 12 to 32.

12+3=15
15+5=20
20+10=30
30+2=32

Another way of looking at it when combining the expressions:

(((12+3)+5)+10)+2=32

12+(3+5+10+2)=32
12+(20)=32

How fingers and toes does it take to get from 12 to 32? Kinda silly if you think about it. 

- - - - -

Let's say it was 32-17=?

I would calculate this in my mind in two ways:

The first would involve two steps by breaking up 17 into 7 and 10. First take 7 from 32 to get 25. Then take the remaining 10 to get the answer 15. 

The second way would involve adding 3 to 17 to get 20, then 12 to get 32 combining 3 + 12 to get 15.

I never used my fingers nor toes to add/subtract and certainly not to multiply ;)

I wouldn't yet fret this form of math.

[firebrand]

I’m not sure the new way is better, but I never really understood what the old method was or why it worked or made sense until 10th grade, when we learned binary and all the other systems and I finally understood on a basic level that the right-hand column was the ones’ place, and the next one over was the tens’ place, etc. I just did it mechanically without understanding why you carried numbers over to the next column on the left.

At least in this new method you are dealing with comprehensible entities. I also have always used something like a previous example (in another thread) as a double check to check that I haven’t made a careless addition error. I add the hundreds, and then the tens, and then the units to make sure the total makes sense.

I think they stopped teaching base-two systems and the like when they figured they had enough computer people, because one time I was checking blues (a late stage of book proof) on someone else’s book and the author had used binary for his chapter titles, just to be a smartass, and many of them were wrong. I explained it to the young woman who was in charge of the project and to her credit she caught on right away, but she had never learned binary before. And neither, apparently, had any of the other people who supposedly checked the book. Maybe they thought that was some kind of design element. It all had to be changed in blues (rather expensive).

[dr_lew]

Yes, but OTOH we see, for first grade:

CCSS.Math.Content.1.NBT.C.4 [...] Understand that in adding two-digit numbers, one adds tens and tens, ones and ones; and sometimes it is necessary to compose a ten.

So in first grade you should learn to reason the 32 is 20 more than 12 right out of the chute.

... and “compose a ten” ??? That’s carrying ! So this dictum pretty much specifies columnar addition, by simple extension.

[Gene Eric]

BTW, these are also valid and similar

12+10=22
22+10=32
--------
   20

12+1=13
13+1=14
14+1=15
15+1=16
16+1=17
...
31+1=32
--------
   20

[RandallFlagg]

That confused me, too.
I just called my 14-year-old, and he showed me how.
How pathetic is THAT?!
;-)

[4Liberty]

What’s silly is that some of the “old fashioned” tables HAD to be memorized in order to get the final solution. Such as 20 + 10.
What- do they think kids are incapable of memorizing the rest of the table??

[deedeedog]

I don’t know how to post. but if people go to “The Daily Caller” and right in Comoncore Math lessons these lessons plans attack Bush, Reagon and list Lincolns religion as Liberal. These also attacks the electoral collage etc. This is is now called Social Justice. You can read about this for yourself and pass this on.

[moose07]

Not at all.
Sounds like sensible use of resources. :)

[Chode]

and that is supposed to be easier than standard multiplication???

[dr_lew]

... the author had used binary for his chapter titles, just to be a smartass, ...

"There are 10 kinds of people, those who understand binary and those who don't."

[RandallFlagg]

This is pretty much me when it comes to math:

[RandallFlagg]

and that is supposed to be easier than standard multiplication???

If you've for a fourteen-year-old handy, it'll help.
It helped me.

[gitmo]

Actually, that’s how cashiers make change. It works if you don’t know how to subtract.

[Praxeologue]

My view is that these new methods are designed to prevent parents from helping their kids with homework. It is another method of exerting state control by removing parental guidance.

Even if you home school, is it not required that students learn in this manner? In that case, it discourages home schooling, since the materials is unfamiliar, to say the least, to parents.

When your child becomes a parent themselves, they will similarly be unable to help or home school their children, since another contortion will, by that time, be invented and imposed by fiat.

[moose07]

Well, I picked it up in 3 minutes, age 14 in year 10.
Depends on how the head is wired. :)