Very cool, basically a visualization of the standard multiplication technique.
For ##x## it really helps for the 2nd step. A number like 18x31 is really quick to do building backwards with this, 8, 25 ,3; so 558. With more rounding, I think my traditional method of rounding and taking into account the difference is better,
99x99 being the worst case example.
I imagine if you practiced even a little you could do 2x2 and 3x3 numbers in a snap.
Cute, but having trouble seeing how that's any better than the grade-school algorithm it's based on. (What, we have to add in unary now? This is progress?) You still have to carry, you still perform n^2 operations for n-digit numbers; the difference is you need a lot more paper and time, and it makes for a better video. (And God help you if you have to multiply any nines...)
Now, someone show me a convolution-based n log n multiplication algorithm you can do quickly with pen and paper and I'll be impressed. :)
For ##x## it really helps for the 2nd step. A number like 18x31 is really quick to do building backwards with this, 8, 25 ,3; so 558. With more rounding, I think my traditional method of rounding and taking into account the difference is better, 99x99 being the worst case example.
I imagine if you practiced even a little you could do 2x2 and 3x3 numbers in a snap.