This is going to be a fascinating math fact. I’ve written about it before. It was on my old, long gone blog, which I deleted several years ago. So, I thought I would repeat it here. As a designer, this fun fact has come in handy many times.
Did you know…?
You can determine whether a number is divisible by the number three just by looking at it, no matter how big the number.
Let’s take the number 498. I can tell immediately whether this number is divisible by three. Simply add all the digits. 4+9+8 = 21. If the resulting answer is divisible by three, then the original number is divisible by three.
The Rule of 3s works with any number. Isn’t that fun?
As far as I know, this doesn’t work for any other number. It would be cool if it did. Try it out! You never know when this information might come in handy.
ETA: Please see comments below. This also works for the number 9. Very cool! Since 9 is 3-squared, I wonder whether it also works for 3-cubed (27), but perhaps that isn’t nearly as handy as 3 and 9.