Posted by Grant Kruger (205.144.232.143) on July 22, 2003 at 20:23:06:
In Reply to: The magic BEHIND the curtain posted by David M Gordon on July 22, 2003 at 14:37:40:
Yikes David - no, I'm no mathematician. I am a little smart though, and it seemed to me that there had to be a simple answer - after all - there is no magic on the web. From there discovery of the ruse was but a fun moment away.
Actually I first was shown this by a fellow programmer who was quite amazed. “Crap,” was my skeptical reply and then of course, I quickly had to prove it (or shut up, which is impossible).
How about this one for you. Ask someone to play this game. Tell them to think of any two digit number where the two digits are not the same (i.e. not 00, 11, 22, 33, etc). Reverse the numbers to create a second number (e.g. if first number is 28 then second number is 82). Tell them to calculate the difference, i.e. subtract the smallest number from the biggest (82 - 28). Now tell them to tell you either digit of their answer and you will tell them the other digit. How? Because both digits will always add up to nine. In our example, 82 - 28 = 54 and 5 + 4 = 9. So if he tells you 4, then you can tell him that the other number is five, and vice versa.
Some more examples:
Diff between 01 and 10 is 09 so 0 + 9 is 9
Diff between 02 and 20 is 18 so 1 + 8 is 9
Diff between 58 and 85 is 27 so 2 + 7 is 9
Diff between 15 and 51 is 36 so 3 + 6 is 9
Diff between 27 and 72 is 45 so 4 + 5 is 9
Diff between 39 and 93 is 54 so 5 + 4 is 9
Diff between 97 and 79 is 18 so 1 + 8 is 9
Diff between 98 and 89 is 09 so 0 + 9 is 9
As you can see, the number nine is a magical number indeed, at least for cyclic two digit equations.
Grant