Most people aren’t that fond of mental arithmetic. There are ways though, how arithmetic can be more interesting. One of those is graphical multiplication:
According to the author of this video, the trick isn’t suited to speed up calculations – it’s merely about motivation.
It’s not a way to make mental multiplications easier, it’s just a fuuny way to resolve graphically a multiplication. It’s only meant to be a little trick to show to friends and kids who hate maths. It’s NOT meant to be efficient as some seems to think. You can do any kind of multiplication with it but yes it’s boring to draw numbers like 8 or 9.
Also interesting is the source of the trick:
My girlfriend learned it from some math teacher during her school years in china. He wanted to make kids interesed in maths and it worked.