Geeky math thing

[Celebration]

I'm a little bit of a numbers freak, and I heard this one from "The Human Calculator." My husband liked it so maybe you guys will too.

Tell someone to pick any two digit number. Then, in their head, they should add the two digits together. If the answer is still two digits, add those digits together, until they come down to one digit.

From the original number that they selected, subract the one digit number they calculated.

Then, with that answer, add those digits together.

Then, say to them--"The answer is nine." It turns out to be nine every single time.

For instance, suppose you chose 76

7+6=13

1+3=4

76-4=72

7+2=9

There you have it. Works with every single number.