[walford]

“No this is a valid mathematical technique. It appears silly in this example because the teacher is using single digit numbers. And yes the student should have been taught from rote memory that 9+6 = 15.”

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The way I was taught long addition as a kid is to take 9 + 6, and just round up the 9 to 10 and take the 1 away from the 6 and add it together. Once you get to the next base 10 number, you take the amount left over after 10 and add it to the next decimal place number. [This is a lot easier to show on a chalk board.] With larger numbers, you do the same thing when computing in your head.

But the way the teacher demonstrated it was nothing like this. She was either intentionally or unintentionally making it more complicated than necessary and ignored the meaning of base-10 numbers.

I maintain that this is deliberately done to bog down the smarter kids.

[UCANSEE2]

She was either intentionally or unintentionally making it more complicated than necessary and ignored the meaning of base-10 numbers.

Maybe it's because the teacher is just as bad at math as her students.

She probably teaches them that the base ten numbering system is made of the digits 1-10.