Thursday, January 17, 2013

Simple Math: Graphical Multiplications

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=?

IMG 6222

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.

IMG 6224

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"

IMG 6225

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.

IMG 6226

1-2-3.  So, the single digit "3" is the addition of the intersections in the lower bottom right group.

IMG 6227

Then, you group the top left group.  And start counting the intersections points.

IMG 6228

1-2-3-4-5.  And you have a "5" in the top left group.

IMG 6229

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".

IMG 6230

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.

IMG 6231

So, the answer is 663.  WOW.

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Let's check it again.  Yup, no doubt.  51 x 13 = 663

IMG 6234

So, if you do a simple single digit multiplication, it works too.  Just count the intersections.

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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.

IMG 6236

Math is a strange thing.  You love and you hate it.  But the world cannot live without it.


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