Date: Jan 17, 2013
I came across this youtube today. I found it very amusing. And I think it is a good way to teach kids too. And this is the way how Japanese teach their kids to do multiplications. Very interesting way, I sua-gu, never learn this method before. HaHaHa
So, I picked up a pen and pencil and trying to test it out.
Let's give myself a not so simple one. 51x13=?
Let's draw 5 horizontal lines plus 1 horizontal line to represents "51". And leave some space between the 5 lines and the single line.
Next draw the 1 single vertical line and 3 vertical lines intersecting the horizontal lines. Again, leave wide space between the 1 line and 3 lines. This is "13"
Now, we start visualise and do the grouping. Basically you can do three groupings. This is the first group. And then, you start counting the INTERSECTION points.
1-2-3. So, the single digit "3" is the addition of the intersections in the lower bottom right group.
Then, you group the top left group. And start counting the intersections points.
1-2-3-4-5. And you have a "5" in the top left group.
Then, there is only one diagonal group. Which is what I have circle in the diagram, so, you count the intersection points. There are 1 and there are 15 so, add up them to become "16".
Every group must be a "Single Digit" number. So, you cannot have "16" in the middle. So, what you do, you move the "ten" or "1" into the left or top group as a single digit and add them up. 进位. So, 5 + 1 (move from the middle group) is equal 6.
So, the answer is 663. WOW.
Let's check it again. Yup, no doubt. 51 x 13 = 663
So, if you do a simple single digit multiplication, it works too. Just count the intersections.
So, if you do a double digit Vs single digit multiplication, it works as well. There is no diagonal group, only two groups, top and bottom. 15 x 3 = 45.
Math is a strange thing. You love and you hate it. But the world cannot live without it.