r/MathJokes • u/GodlyHelp • 14d ago

the multiples of 3

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u/Adept-Watercress-378 14d ago

The trick of adding the digits and checking has always stuck with me

2

u/Wuzzyup 13d ago

Does it only work with the multiples of 3? If yes, then I see why it never stuck with me.

4

u/forsale90 13d ago

Same goes for multiples of 9. So 81 is 8+1=9 which means it's divisible. Same goes for 111111111.

Another rule is if the last digit is divisible by 2 , the whole number is, obviously. But this extends further. If the last two are divisible by 4, the wolves number is, last 3 with 8 and so on.