John Heaton (jheaton) wrote,
John Heaton

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Fun with arithmetic

So over on Tumblr, someone posted this, which you may well have seen somewhere before:

It's said that 98% of people who follow these instructions will think of Denmark, a kangaroo, and an orange. For my own part, I thought of Djibouti, an impala, and an apple, but that's mostly because I'd seen it before and I remembered the common answers. I'm not sure what I'd do if I had to do it a third time. Dahomey isn't a country any more, and off the top of my head I can't think of any other countries starting with D. (Having looked it up, there are two I had forgotten: Dominica and Dominican Republic.) That's the trick, you see; the result of step 5 is always the letter D, thanks to an interesting principle that was pointed out to me in grade school: when you multiply any number by nine, the digits of the product will always add up to nine. For example:

9 x 7 = 63
6 + 3 = 9

For products with more than two digits, you may have to do a second round of addition:

1066 x 9 = 9,594
9 + 5 + 9 + 4 = 27
2 + 7 = 9

But eventually you'll always get down to nine. Which is why this smug response from a Tumblr user who reblogged the above amused me so much:

an ant in canada eating a tangelo

~fuck you statistics~

To which I can only say:

Dear Tumblr user:

No, fuck you.

Love, arithmetic


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