>>7641586 So that's what that fucking lecturer was doing. Some intro maths lecturer at my Uni was trying to show something like that and everyone was confused as fuck. Didn't help that the guy was ESL.
>>7641565 Common core is written mental math for retarded people that can't into mental math by themselves ( and generally it just ends up confusing them just as much if not more, as their retardation is genetic and not due to a flawed teaching method ).
>>7641565 Those two ways are literally the same thing, the second is just made more explicit. What's happening is they start at 12 then preform a series of smaller steps to reach 32, they then add up these smaller steps and that gives the difference between the two.
>But the way I learnt is easier, this is pointless.
They way you learnt it works for simple problems, when you take it to something larger, it becomes very cumbersome for mental arithmetic.
The idea is to regroup your numbers into things that can be easily done in your head, multiples of 5s or 10s or whatever. It's how everyone who is any good at mental arithmetic does it.
All the people who bitch about common core simply don't understand it. They're like programmers who still refuse to code in anything but assembly, using nothing but algorithms that were devised back before the transistor was invented.
In the subtraction problem shown, it's taken that it's easier for most people to add than to subtract. So you start at 12. Add 3 to get to a multiple of 5. Add 5 to get to a multiple of 10. Add 10 until you get close to the answer. And then add whatever's left.
Do it in your head. "12, 3 (makes 15), 8 (makes 20), 18 (makes 30), and 2 gives 20."
But maybe you're not convinced by small numbers. Try it with 73299 - 4573.
4573, 2 makes 4575, 7 makes 4580, 27 makes 4600, 427 makes 5000, 5427 makes 10000, 65427 makes 70000. > at this stage, the problem is reduced to adding 65427 and 3299 > I'd add 3300 and subtract 1 > common core teaches you to think about how it works, so you can invent improved methods like that on the fly 65427 + 3300 = 68727, minus 1 gives 68726
You can do it in your head, without risk of error from carrying (which is really counter-intuitive to a lot of people), and you can do it with really big numbers.
>>7641656 Now, a person well versed in this method will come up with their own optimizations, things that are easy and intuitive for them. It's not one size fits all. It's not supposed to be. 73299 - 4573 > I can happily see that 4573 > 3299, so I'll start by adding 60000. Actually, I like to subtract here, for reasons that are my own. It doesn't matter. It's flexible. I say "6" > and I am left with 13299 - 4573 > I want to add 13 - 4, but see that 573 > 299, so I only add 13 - 5 "8" > and I am left with 1299 - 573 > actually, I'm just going to do 1300 - 573, then subtract 1 at the end. I can do this in my head directly, but for completeness I might count like this if I'm tired or something. > 573, and "7" > makes 1273, and "2" > makes 1293, and 7-1 is "6" "68726"
It gets even better when you start doing multiplication, division, or roots. Can you calculate 5th roots in your head? I can, and I'm kind of a dumbass. But it's all the same idea.
are you all fucking retarded? if I want to calculate 86 - 32 32 + 8 = 40 40 + 40 = 80 80 + 6 = 86 so it's 54 they just added in a step to get to the 5 so it's even easier. it's not slow, it's not "fuckery". it's intended for doing substraction in your head and it's a great method. I mean, who doesn't do it? when i substract I imagine this in my head.
Common Core is a set of standards; that's it. It is a guideline for establishing what kids should know/be practicing in what grade.
You can see the goddam standards for yourself: http://www.corestandards.org/Math/
NOWHERE does it dictate HOW the standards should be taught; only that they should be.
If some pants-on-head liberal douchebag wants to teach kids how to add and subtract in the most dumb-ass way possible, that is the prerogative of that teacher/school/district.
Personally, if my kid brought this home, I'd show them how I did it, then let them figure out which method they liked better. And if the teacher threw a fit, I'd pull my kid out of that school and find someplace that doesn't treat children like retarded monkeys.
Thread replies: 28 Thread images: 2
Thread DB ID: 76791
All trademarks and copyrights on this page are owned by their respective parties. Images uploaded are the responsibility of the Poster. Comments are owned by the Poster.
This is a 4chan archive - all of the content originated from them. If you need IP information for a Poster - you need to contact them. This website shows only archived content.
If a post contains personal/copyrighted/illegal content you can contact me at email@example.com with that post and thread number and it will be removed as soon as possible.