Double monodigital sighting really rare

0 Comments | Deseret News (Salt Lake City), Feb 9, 2006 | by Bill Sones

Question: From a Utah reader: "My husband and I were driving when he happened to spot the odometer reading 22,222. Then we drove immediately to a store where we made multiple purchases and, yup, at the checkout the total was $222.22. We are wondering: Is there any way to figure the odds of the numbers coming up like this?"

Answer: There are lots of possible assumptions and answers, suggests University of California-Los Angeles mathematician James Ralston. For example, ignoring the decimal and assuming all five- digit numbers between 10000 ($100.00) and 99999 ($999.99) are equally likely, the chance is 1 in 90,000, since there are 90,000 such numbers.

If you broaden this to include the UNLIKELIHOOD of spotting the 22,222 on the odometer, things get even more interesting. Let's call these "monodigital" readings, says College of Charleston mathematician Alex Kasman. The probability of spotting one of these at any given time is small. Starting out, a car runs through 11 miles, 22, 33 . . . 111, 222, 333 . . . and so on. Drive 100,000 miles and you'll turn over 36 monodigitals. "They're certain to occur, though you probably won't notice most of them."

Now suppose you make a game of watching for these, and every time you spot one you pull over to make some random purchases. Can you reproduce the checkout feat of the Utah reader? Not likely, but not impossible either, says Kasman. If you spend $10 to $1000, there are four monodigitals -- $22, $22.22, $222 and $222.22 out of 99,001 possible prices -- to match 22,222 miles. Thus the probability is 4/ 99,001, or just a bit more than a one-in-25,000 chance.

Probably the game will drive you crazy first. . . .

Question: Who sent the world's first e-mail?

Answer: If the question means "who sent the first message over a network from one computer to another computer?," then Len Kleinrock - - UCLA professor and one of the inventors of Packet Switching -- lays claim to this, though it is not known for sure, says computer scientist Alan Kay of UCLA, MIT and Kyoto University. This was done on the old ARPAnet, which became the Internet and which first started up in September 1969.

However, sending messages to others, including instant messaging and chat, appeared much earlier on the first time-sharing systems, says Kay. These were big mainframe computers that could handle 100 or more users at a time communicating with the mainframe via typewriter terminals. One of the earliest was CTSS at MIT, circa 1963. Another was Project Genie at Berkeley. Both had e-mail, IM, and chat. So why did it take so long for e-mail to catch on? "Quite a few people have to believe something is normal before it becomes normal -- a sort of 'voting' situation. But once the threshold is reached, then everyone demands to do whatever it is."

Gotta go now to check our e-mail.

Send STRANGE questions to brothers Bill and Rich at strangetrue@compuserve.com, coauthors of "Can a Guy Get Pregnant? Scientific Answers to Everyday (and Not-So- Everyday) Questions," from Pi Press.