mental math

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DNS
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mental math

Post by DNS »

Nas Daily's video today:



That's the way I would add too, but I'm no where as good as this guy. The key is just going left to right. For example:

54
+47
+63
+75
======

Just add up the left column first:
50+40+60+70 =220 (whole, round numbers easy to do in your head)
then the right column
4+7+3+5=19

220+19=239

Easy, once you know the trick.
Miorita
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Re: mental math

Post by Miorita »

It's called Arithmetic.
:anjali:
Miorita
Last edited by Miorita on Sat Feb 20, 2021 7:13 pm, edited 1 time in total.
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Re: mental math

Post by DNS »

Miorita wrote: Sat Feb 20, 2021 7:10 pm It's called Arithmetic.
:anjali:
Miorita
Correct, the more advanced math is what is really math; trigonometry, calculus, etc.

But in colloquial usage, people refer to it as math or in this case, mental math; doing the arithmetic in your head, no paper, no pencils.
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Nicholas
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Re: mental math

Post by Nicholas »

The point Miorita missed, (for the only time of course) is that Arithmetic was taught until recently thusly:

54
+47
+63
+75

Add the right column first, 4+7+3+5=19 - then put down 9 only and carry the 1 to the top of the left column. Then add those four digits to the 1 and get 23 which you write down to left of the 9, voilà = 239.

But this new method is quicker, unless you are used to the way you were taught as a child.
Dhamma is against the stream of common thought, deep, subtle, difficult, delicate, unseen by passion’s slaves cloaked in the murk of ignorance. Vipassī Buddha
Miorita
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Re: mental math

Post by Miorita »

He does this out of fear.
In case anyone catches him, he tells them he's done his math.
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Re: mental math

Post by DNS »

Miorita wrote: Mon Feb 22, 2021 6:57 pm He does this out of fear.
In case anyone catches him, he tells them he's done his math.
Fear of what? No, I think he's just good with numbers and the mental way of doing it left-to-right. With practice, one can get pretty good at it, although I don't know if there's anyone better than this guy (in the video).
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Re: mental math

Post by DNS »

When my kids were young, I'd play a game with them:

Start with 2.
Double it. (no paper, no pencils)
Have a referee who checks with calculator.
Keep going until someone gets the wrong answer.
For example, 2, 4, 8, 16, 32, 64, 128, 256, 512, 1024, 2048, 4096, 8192, etc.
Sometimes we'd get up to 524,288 and then one of us messes up.
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