Well fuck my life if only I had known this in school >_____<
This is something I will teach my children.
This is a SUPERIOR method of multiplication and if I had known this before, omfg.
I might not have failed math three times.
omfg this is amazing my child will learn this yep.
Mind = blown
When I’m awake enough to have any brain power left I’m figuring out why this works, unless it’s a rather basic thing that I should be seeing but am overthinking. Right now I’m fumbling with possibilities of array and place value and squinting at the screen to see where things fit.
Okay, got it. It’s basically the same principle as is behind: (a+b)(c+d) = ac+ad+bc+bd To use their example: 21*13 = (20*10) + (20*3) + (1*10) + (1*3) = 200 + 60 + 10 + 3 = 200 + 70 + 3 (This is the step that they “jump to” after counting the dots) = 273 You do have to be careful if multiplying numbers with different numbers of digits, though. It still works, but is complicated a tiny bit. You have to be more careful again, when multiplying a value with one of its digits as 0. But overall, I really like this process. It doesn’t have a whole lot of use in secondary maths (as most students should really have calculators), but could be an interesting and fun exercise to try.