No.So... what's the point here?
I'm guessing it lampoons how the teacher established a "pattern" that's technically correct, but didn't really explain the concepts (e.g., multiplication and division) beyond just some ad-hoc ratios, which is no way to teach math.
No.
It takes Marie ten minutes to saw through the board once. To cut it in three pieces, she has to cut through it twice. Working just as hard, that takes her twice as long as doing it once = twenty minutes.
The kid got it right, the teacher is an idiot.