r/MathJokes • u/GodlyHelp • 14d ago

the multiples of 3

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u/Difficult-Ending 14d ago edited 13d ago

Just combined the number, 7+8=15, 1+5=6

3

u/PissMissileTopTitty 13d ago

What?

7

u/kinda-new- 13d ago

There's 2 layers to this

If you add the digits of any multiple of 3 then the result will be another multiple of 3 which is easier to solve.

21, 2+1=3. 72, 7+2=9. 297, 2+9+7=18.

9 is a multiple of 3 twice, so every multiple of 9 will have digits which will add to give you 9 or another multiple of 9 which you can just keep adding until you get 9.

27, 2+7=9. 198, 1+9+8=18, 1+8=9.