The Puzzler #18

THIS MONTH'S CONTEST
HOTEL KEY CODES

Modern hotels change the codes assigned to individual rooms every day. For security reasons, a hotel “encrypts” the door code based on the corresponding room number. Below is a list of room numbers with the corresponding key codes. Your challenge is to break the formula so you can determine the key code corresponding to room 278 and the room number corresponding to key code 364.

Please email your solution to John Kador [email protected] using the subject line “Hotel Key Codes.” Deadline is April 25, 2010. Two responses will be selected to receive a signed copy of John Kador's How to Ace the Brainteaser Job Interview. Good luck.

BRAINTEASER: UNITS OF TIME

As Registered Rep. readers, you work with units of time every day. But there are many ways to define time. Try these brain teasers (answers at bottom of page).

1. Try your skill at defining these units of time.

   1. A Microsecond is what fraction of a second?
   2. A Lustrum is how many years?
   3. Ephemeral is how long (by definition)?
   4. A sesquicentennial is how many years?

2. Order the following from longest to shortest: Epoch, era, period, eon.

SOLUTION TO PREVIOUS PUZZLER: 907 PRIME

To recap: Consider these three statements: Alice says Bob lies. Bob says Craig lies. Craig says both Alice and Bob lie. Who lies and who tells the truth?

Solution: Bob is telling the truth. His is the only non-contradictory statement. Alice and Craig are lying. We received over 100 responses to this classic truth-and-liar problem. Only half the responses were correct. Some readers examined all possible cases. Others solved the problem by inspection. Congratulations to this month's winners, who offered the most elegant explanations:

Michael S. Stickler, Senior Vice President, Morgan Stanley Smith Barney, Short Hills, NJ

Eduard David Yankovich, CFP, Brooklyn, NY

SOLUTION TO UNITS OF TIME: 1a. A microsecond is one one-millionth of a second; 1b. A Lustrum is five years.

1c. Ephemeral is 24 hours; 1d. A sesquicentennial is every 150 years; 2. Eon, era, period, epoch.

John Kador is the author of 10 books. His latest book is Effective Apology: Mending Fences, Building Bridges, and Restoring Trust (Berrett-Koehler). www.effectiveapology.com