Just in time for Halloween, and it’s down right scary.
Your computer is going to read your mind!
http://www.learnenglish.org.uk/games/magic-gopher-central.swf
Well, the computer, of course, is not reading anyone’s mind.
There’s a neat trick in math where subtracting the sum of the digits of a two-digit number from itself always equals a multiple of 9.
So, for example if you have 43, then 43 – 7 = 36. Or 28-10=18, 57-12=45, 32-5=27, etc etc etc
Now look at the symbols in the game for 9, 18, 27, 36, 45, 54, 63, 72, 81, 90, 99. They’re all the same, ain’t they? All the other symbols are just filler to fool you.
Now that you know how it works (and Knowledge is Power, I always say) you can go and impress your friends.
There are lots of cute tricks with the number 9 — such as adding the two digits themselves in the multiples of 9 (i.e., 18, 27, 36, 45, 54, 63, 72, 81, 90) also equal to 9. And these multiples are palindromes (”mirror images”) of another multiple. So 45 is a palindrome of 54, 36 is a palindrome of 63, 81 is a palindrome of 18, etc.
These weird properties of 9 is the reason why the ancients thought 9 had mystical powers and associated it with the occult and witchcraft.
Blessed be!
Tags: fun science