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Comment by nodata | Hacker News Reader

Well what are the four ways to do addition?

1) "counting on". 19 + 7 is (starts counting on) 20, 21, 22, 23, 24, 25, 26 (realise that 7 fingers have been used, stop counting on) 26

1a) "partitioning" 8 + 7 is 8, jump 2 to 10, then jump 5 to 15.

2) "thinking and estimating". 3998 + 4997 is nearly 4000 + 5000 and is exactly 4000 + 5000 - 5

3) traditional columns with units, tens, hundreds, etc.

Note that these are teaching small children how to manipulate numbers in their heads before they reach for paper and pencil. This builds up understanding of what numbers are, what the processes are doing, what the relationships between numbers are etc. these techniques are also building up skills for subtraction. Subtraction is not just "taking one number from another", it includes finding the difference between two numbers and techniques involve addition.

So they are being taught some optimisations that they'd normally learn later? Doesn't sound too bad.

Problem is some optimizations (like the "estimation" approach) require an innate grasp of non-optimized methods. If you don't understand what's being optimized, the optimization makes no sense.

1. 5+9=14

2. let 9=10-1, 5+9=10-1+5=15-1=14

3. let 9=5+4, 5+9=5+5+4=14

4. cann't make it up

I truly pity the youth in whatever country thought that is smart

you missed two most important methods:

5+9 = (((((((((5+1)+1)++1)+1)+1)+1)+1)+1)+1) 5+9 = 9 + 5 =...

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