
Chika's Test (For Divisibility by 7) - acidflask
https://www.westminsterunder.org.uk/chikas-test/
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gus_massa
The link to the proof is [https://www.simonellismaths.com/blog/new-
maths](https://www.simonellismaths.com/blog/new-maths) (the link in he article
says "post" instead of "blog"). It's standard modulo arithmetic, but it's nice
to see a rediscovery by a kid.

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zamadatix
Fun story showing how it's more fun to find things in math than just be told
them. I think if more people had this kind of experience there would be a lot
less hate on math! I have to say I like the subtraction method mentioned more
though, both sides of the number end up staying smaller making it quicker to
converge and calculate.

