Clever Multiplication Technique (Video)

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.

Turns out this isn't 'new' by any means, but it is definitely cool. (i have no evidence to back up this statement other than childhood memory)

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. :)