Tuesday 21 February 2017

Maths Tricks To Teach The Kids

I was never a big fan of Maths at school, I had one great teacher at high school, she was that good that I actually understood everything she taught, aced my exams and got me into the top class the following year. That turned out to be my downfall because I didn't understand anything the next teacher taught.

For maths I need to see every step and it wasn't until a few years later when I was at college that I figured out that was the reason I never understood Mr Murray's class. He would skips steps that he assumed everyone would know.

I was always under the impression that I was crap at maths because as a kid, that is what I was constantly told. BUT when I was 18 I applied to get on a government run scholarship, at that point I had done a year at art college then a year at tech doing an engineering foundation course. I had not got A level maths or physics and hadn't studied the curriculum.

Nether the less I managed to get an interview for the scholarship and then we had to sit some tests. I was the only one in the interviews that hadn't done A levels or the Scottish equivalent yet I aced the test and got the top score on my maths!

And yes, I got the place, there were just 60 in the whole country so it was a pretty big thing for me.

The point of this story is that I struggled at school and was led to believe that there was only one way to get the answer, this appears to be another deception! When I look at Ebi-kun's maths book I am often baffled at the way he has been taught to find the answer, it doesn't feel logical because it's not the way I was taught. It doesn't make it wrong and I do like the fact that he is taught different methods to reach the same answer.

I think the bead material that is used in Montessori hit a chord because I wish I had been taught in that logical way, I still love the Montessori maths materials and I'm sure it is down to that, that Ebi-kun has a strong foundation for his maths.

Anyway, this might be old news to you but for me, this trick made me very happy! I discovered the Trachtenberg method, Ebi-kun loves the idea, so I'll hare each trick on here as I teach him.

Challenge #1 - Multiply by 11

3 2 4 x 11

Imagine the number is is actually written:

     0 3 2 4 0

Start from the right and work to the left, add the first number to it's neighbour, the 2nd number, and write the answer below the 2nd number

     0 3 2 4 0  (0+4)

Then add the 2nd and 3rd numbers...

     0 3 2 4 0  (4+2)
           6 4

And continue along the row of numbers adding the next to it's neighbour...

     0 3 2 4 0  (2+3)
        5 6 4


     0 3 2 4 0  (3+0)
     3 5 6 4

Easy-peasy right? But what if you use numbers that carry over. Well then you do the same as normal, carry the ten over to the next number, represented by a * here

437440 x 11

     0   4   3   7   4   4   0

     0   4   3   7   4   4   0
                         8   4

     0   4   3   7   4   4   0
                  *1   8   4

     0   4   3   7   4   4   0
             *1 *1   8   4

     0   4   3   7   4   4   0
          8 *1 *1   8   4

     0   4   3   7   4   4   0
     4   8 *1 *1   8   4

therefore 437440 x 11 = 481184

The best thing to do is try a few out for yourself. When we showed this to daddy, he had another method which was similar but involved an extra line of numbers.

Ebi-kun pointed out that at school they have to show the workings out so that the teacher could see how they have arrived at the answer, which is fair enough. But I still think it is valuable for kids to know that there isn't just one way to do something.

There are quite a few of these tricks in the Trachtenberg method so as we work through them I'll share what we are doing. Who would have thought I found maths fun!  Not me!!

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