The terms used to explain some of it are poor metaphors but what they do is solid.

First is shown using binary (mixed with decimal but not) to multiply and divide and then the same only a different way.

To multiply 17 by 25

## 17 x 25 ← left value then as binary, right value doubles every line

##
1x1 25

2x0 50

4x0 100

8x0 200

16x1 400

= 25 + 400 = 425 <— then add the right column values that the left has 1’s not 0’s

17 x 25 = 1 x 25 + 16 x 25 = 425

Division goes the other way as they show.

I haven’t taken the time to proof the second method they show, need to work out the part of crossing out evens.

There are other fast math videos worth watching, algorithms to be gained!