Isn't this a bit like using an abacus? My third grade teacher used what she called a "20-counter abacus" which was basically some hoops placed over a board, with different colored discs for each numeric place. She would have placed the discs on the front side just as the shapes are shown here.
I would avoid geometric shapes, just so two different kinds of math don't get mixed. I would also avoid those colors because especially during the elections we see a lot of red and blue everywhere, and turning off of that likely helps students focus better on the math. In the worst case scenario, someone could point out how the black borrow from democrats. It's a teacher's nightmare to have to recover from spontaneous chaos in class. You could use stickers with the presidents found on each bill: 100 (Franklin), 10 (Hamilton), 1 (Washington). This would facilitate learning something useful outside the math class too - financial education, history.
different shapes and different colors .... WTH, So how the hell is black circles ever equal to something red or blue with flat sides? Created by simple evil . I'm an electronics eng. and this would have twisted my brain up when i was a kid.
I mean it literally is just a bad visual representation of how you would usually do subtraction with numbers on paper, except going left to right, instead of right to left like a sane person.
So...using 3 minutes to explain something we learned in 30 seconds is better? Also I came here from the question "Explain how 2/3's is different from 4/6's" video which I mean obviously its the same.
