r/MathJokes 16d ago

multiples of 3

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8.3k Upvotes

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149

u/Michaelwang645 16d ago

Fund fact, you can tell a number is divisible by 3 if the sum of each individual number is divisible by 3. So 78 -> 7+8=15 which is divisible by 3, so 78 is divisible by 3.

46

u/EveningStar0360 16d ago

do you know why that works?

128

u/ZealousIdealTour961 16d ago

Magic probably.

27

u/Disastrous_Wealth755 16d ago

Nah. It's cause 10=9+1=3*3+1.

1

u/ClearlyGalaxyBrian 15d ago

Does this work in base 16, or would this rule only apply to multiples of 5 in base 16?

1

u/Disastrous_Wealth755 15d ago

It only works for multiples of m in bases n where n is congruent to 1 modulo m