Amazing Trick

Try this:
http://digicc.com/fido/

I’m going to ruin it, but it’s a mathematical fact that when you subtract the smaller number away from the larger number, where all four digits are the same, the resulting digits will always add up to multiples of 9. By telling Fido Dido the other three digits, the site is programmed to add those three and subtract them from a number that is divisible by 9 – giving you your remaining number.

Pretty cool.

Who knew maths would get so many people clicking on a web site?

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