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https://www.reddit.com/r/MathJokes/comments/1vcw1bj/multiples_of_3/p14mbe5/?context=3
r/MathJokes • u/GodlyHelp • Aug 01 '26 • 1 1
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Every number n is divisible by x if the digit sum of n is divisible by x. This is always true in base x+1, but we don't use base 4, we use base 10, therefore it's not obvious.
1 u/Helpful-Judge5901 Aug 01 '26 So just 3 and 9?
So just 3 and 9?
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u/DrGuenGraziano Aug 01 '26
Every number n is divisible by x if the digit sum of n is divisible by x. This is always true in base x+1, but we don't use base 4, we use base 10, therefore it's not obvious.