Why we teach

Let x = 0.222 ...

On Friday, after lessons, a pupil came to find me. I don’t teach him this year, but have done so previously and I know him to be particularly interested in the subject and we often chat about what he’s currently studying in maths.

He sought me out for some help with a problem he had encountered: write 0.2 recurring as a decimal.

So we grabbed a scrap of paper and pencil and ‘did the math’ as they say in America:

Let x = 0.2222 … recurring

Multiply x by 10 to give:

10x = 2.222…

Now subtract x from 10x:

 10x = 2.222 …

 – x = 0.222 …

 9x = 2

So 9x = 2, therefore

x = 29

I’ve always found this a neat little piece of maths, and my student did too.

And that’s two reasons why we teach:

  1. We get to use maths on a daily basis, and still get a buzz out of its simple brilliance.
  2. Sharing that knowledge with young people and helping them make sense of the world around them.

A great way to end the teaching week!

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