

stanalger Special user St. Louis, MO 996 Posts 
I'm posting this in "Puzzle me this..." because I'm not sure
this "trick" is worthy of being considered "magic." It reeks of math...and its conclusion (although mysterious) is anticlimactic. But I'm sure some of you will find it quite interesting. Perhaps one of you can help me transform this into something better. But first...a demo.  Grab a pencil (pen), paper and calculator. (A simple four function, eight digit readout calc. works best. If you have something fancier, that's OK. But the calculator on your cell phone will do just fine.) Turn the calc. on and hit the CLEAR key. You're now going to create a PIN. You can write it down somewhere on your piece of paper... or not. (It's not at all important that you remember the PIN. You won't be asked to use it again. But if you choose to keep track of all your steps, please doublecheck these steps for accuracy before responding.) My bank's ATM requires me to use a 4digit PIN, but I want a bit more security than that. So please choose a 5digit PIN. Enter your PIN into the calculator. Now multiply your PIN by the number of days in a week. (We're working with the Gregorian Calendar throughout this trick.) Next multiply THAT product by the number of months in a year. (Your calc. should now be displaying a 6 or 7 digit number.) The number on your calc's screen will serve as an "encryption number." Now I want you to choose any date that has occurred/will occur in your lifetime. (This works for any date between 01 Mar 1900 and 28 Feb 2100.) On your paper, write down the day, the month, and the year (19002099). Use all four digits for the year. Use "little endian" format: [D month YYYY] or [DD month YYYY]. (http://en.wikipedia.org/wiki/Calendar_date) This format is common to the vast majority of the world's countries, but it may seem strange to some of my fellow U.S. citizens. Examples should make things crystalclear: 31 January 2075 (NOT January 31 2075) 3 May 1956 16 Aug 1999 Circle this date on your paper. We're going to modify that date before entering it into the calculator. First, we need to turn the month name into a special coded digit. Beneath the name of your month write the digit that corresponds to that month according to the following correspondence: Jan4 Feb6 Mar3 Apr5 May4 Jun6 Jul5 Aug7 Sep9 Oct1 Nov3 Dec2 Second, IF your chosen date falls in a January or February, please subtract 1 from the year. Write the "reduced" year below the original year. (If your chosen date falls in one of the other ten months of the year, let it be.) Now combine the digits of the (modified) date to form a 6 or 7 digit number. You simply run the modified date numbers together to form one long string of digits. Day digit(s)...followed by month digit...followed by the four year digits (less one for Jan/Feb). So: 19 Feb 1960 would become the 7digit number 1961959. (Feb has been replaced with a 6...and 1960 was decremented to 1959.) 6 Sep 2076 would become the 6digit number 692076. (Sep has been replaced with a 9...and the year was not changed.) Got it? Recap: You've got a 6 or 7digit number in the calc. (There's no way I could know this number.) You've got a date written on your paper. (There's no way I could know this date.) And you've encoded your date as a 6 or 7 digit number. Okay. The hard work is done. That wasn't so bad, was it? We have only a bit more work to do. Add your encoded date number to the number already in the calculator. Got it? If so, the calculator should now be displaying the sum, a number that may have up to 8 digits. Even if you gave me this number, there's no way for me to use it to figure out your original PIN...or the date you have in mind. If I knew the PIN, I could easily determine the date. If I knew the date, I could easily determine the PIN. But since I know neither.... One last calculator step. Divide the number on your screen by 7. The calculator now displays a string of digits. PM me the two digits immediately preceding the decimal point and the digit that immediately follows the decimal point. (If the screen shows 1656042.1756, PM me the number 42.1 If the screen shows 1065106.27783747327, PM me the number 06.2 If the screen shows 456657 (a whole number), PM me the number 57.0) Do not PM your PIN...or the resulting encryption number... or the date. Only PM the three requested digits. But keep all the other info near your computer. Stan Alger 
stanalger Special user St. Louis, MO 996 Posts 
Quote:
On 20070105 11:16, stanalger wrote: Thank goodness I'm not a salesman. I thank the very few who gave this a try. I will continue to respond to PMs sent by any future participants. Stan 
bmusiker New user 1 Post 
My number is 58.0
Please enlighten me with the how in addition to your answer. BJM 
stanalger Special user St. Louis, MO 996 Posts 
BJM,
Check your PMs. (If you're logged in at the Café, you'll see a box near the upper righthand corner of this page notifying you that you have a Private Message. Click on that box. I mention this 'cuz I see this is your very first post to the Café.) Stan 
stanalger Special user St. Louis, MO 996 Posts 
I've received a sudden flurry of PMs with regard to this.
Strange. It was all but ignored when it was first posted. Maybe students are just now getting back to their computers after winter break. Speaking of winter, there's supposed to be an icestorm headed my way. This means my power may go out. So if you send a PM...and don't get a timely response, please be patient. Stan 
Steve Martin Inner circle 1119 Posts 
Stan  that was quite clever. I can see how you get the answer, but not how you deduced my phone number at the same time.
Any man who reads too much and uses his own brain too little falls into lazy habits of thinking.
Albert Einstein 
stanalger Special user St. Louis, MO 996 Posts 
Steve Martin,
You are a wild and crazy guy! 
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