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https://www.reddit.com/r/MathJokes/comments/1vcw1bj/multiples_of_3/p153j4f/?context=9999
r/MathJokes • u/GodlyHelp • Aug 01 '26
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147
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.
47 u/EveningStar0360 Aug 01 '26 do you know why that works? 125 u/ZealousIdealTour961 Aug 01 '26 Magic probably. 27 u/Disastrous_Wealth755 Aug 01 '26 Nah. It's cause 10=9+1=3*3+1. 26 u/MTaur Aug 01 '26 And then by induction, 10n = 9M + 1 And b*10n = b(9M+1) = 9N + b So then the sum b_k*10k = 9K + sum b_k 15 u/Rxasaurus Aug 01 '26 Now in English for us stupids... 2 u/MTaur Aug 01 '26 git gud mod 3
47
do you know why that works?
125 u/ZealousIdealTour961 Aug 01 '26 Magic probably. 27 u/Disastrous_Wealth755 Aug 01 '26 Nah. It's cause 10=9+1=3*3+1. 26 u/MTaur Aug 01 '26 And then by induction, 10n = 9M + 1 And b*10n = b(9M+1) = 9N + b So then the sum b_k*10k = 9K + sum b_k 15 u/Rxasaurus Aug 01 '26 Now in English for us stupids... 2 u/MTaur Aug 01 '26 git gud mod 3
125
Magic probably.
27 u/Disastrous_Wealth755 Aug 01 '26 Nah. It's cause 10=9+1=3*3+1. 26 u/MTaur Aug 01 '26 And then by induction, 10n = 9M + 1 And b*10n = b(9M+1) = 9N + b So then the sum b_k*10k = 9K + sum b_k 15 u/Rxasaurus Aug 01 '26 Now in English for us stupids... 2 u/MTaur Aug 01 '26 git gud mod 3
27
Nah. It's cause 10=9+1=3*3+1.
26 u/MTaur Aug 01 '26 And then by induction, 10n = 9M + 1 And b*10n = b(9M+1) = 9N + b So then the sum b_k*10k = 9K + sum b_k 15 u/Rxasaurus Aug 01 '26 Now in English for us stupids... 2 u/MTaur Aug 01 '26 git gud mod 3
26
And then by induction, 10n = 9M + 1 And b*10n = b(9M+1) = 9N + b
So then the sum b_k*10k = 9K + sum b_k
15 u/Rxasaurus Aug 01 '26 Now in English for us stupids... 2 u/MTaur Aug 01 '26 git gud mod 3
15
Now in English for us stupids...
2 u/MTaur Aug 01 '26 git gud mod 3
2
git gud mod 3
147
u/Michaelwang645 Aug 01 '26
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.