9 is not a Magic Number

Someone once told me that today, 09/09/18 was a significant date, because nine is such a special number. (18 being two nines)

And in a way, yes it is. I have always loved the number nine. Nice and round but with a “tail”. 9

An upside six.

999 for emergencies.

The last single digit before 10.

And there’s of course the cute maths trick of the number nine. Multiply it by any number, add up the digits of the answer, keep going till you have a single digit, and that digit will be the number nine.

Eg 9 x 5 = 45. 4+5=9

9 x 15 = 135. 1+3+5=9

9 x 276 = 2484. 2+4+8+4= 18. 1+8=9

And so on. Try it. It works every time, no matter what number you pick.

But there’s nothing “magic” about it. It happens to work for number 9 because we use the decimal system, which uses 10 as a “base” (B) This “mathematical trick” would work equally for other numbers if we used systems based around other systems other than the decimal one. The number in each of those cases would be B-1.

For example, in a system based on sixes, B-1 would be 5 and hence 5 would be a “magic” number. For those based on 12, 11 would be “Magic”.

All of this is better explained by this blog post . Do please read it for an explanation of how this all works. And shows other curious properties of the number 9.

But, seeing we live in a world that uses the decimal system, I suppose today could be some sort of significant day. And since I’ve been thinking a lot lately on the tragedy of the massive suicide rate amongst autistics, I would like to dedicate today to all those autistics who could no longer stand being in this world and who opted out.

Yeah, quite a morbid way to end this post but sometimes I’ve no idea the twists and turns a blog post will take until I write it.

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