Japanese multiplication technique - GIF

[mklotz]

Looks nice. Try 76x47...

Or 99 x 99.

Gonna be drawing a lot of lines and counting a lot of intersections. I fail to see any advantages to their system.

99 x 99 = (100 -1) x (100 -1) = 100 x 100 - 200 + 1 = 9800 + 1 = 9801

would seem a lot simpler - can even do that one in your head.

76 x 47 = (80 - 4) x (50 - 3) = 4000 - 240 - 200 + 12 = 3560 +12 = 3572

Ok, a bit more difficult but still simpler than drawing all those lines.