Scientific American presents Math Dude by Quick & Dirty Tips. Scientific American and Quick & Dirty Tips are both Macmillan companies.

Pick a number, any number. Then multiply it by 9. Next, add its digits together and keep doing that with each successive number you get until you end up with a single-digit number. Now subtract 5.

Find the letter corresponding to your number—where 1 is A, 2 is B, and so on—and think of a European country that begins with that letter. Take the last letter of that country and think of an animal that begins with that letter. Finally, take the last letter of that animal and think of a color that begins with that letter.

I bet you're thinking about orange kangaroos in Denmark.

Am I right? Indeed, the results are in and math fans around the world have responded almost unanimously that orange kangaroos in Denmark is exactly what they get.

As we began to talk about in Part 1 of this series about the number 9, it wasn't magic that let me know this, it was the amazing properties of the incredible number 9—properties that are used over and over again in lots of seemingly magical math tricks. Want to know how it works? Keep on reading!

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