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A little Wizardry for ya

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In maths... (too geeky?) :confused:


A 2-digit number can be represented by digits a and b.


So our initial number:

x = 10a + b


The sum of digits:

y = a + b


Our final number:

z = x - y

z = (10a + b) - (a + b)

z = 10a + b - a - b

z = 9a


Therefore the final number is independent of b, and only dependent on a multiple of 9, hence wot people said before.


Clever though. I was convinced it was magic for a while... :D

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