Think you're smart? Smart enough to work at the country's best corporations. (Oh, you already do?) OK, let's put you to the test. “The Puzzler,” an occasional column appearing in this space, offers real-world brainteasers that recruiters use to assess the brainpower of job candidates at major companies like Microsoft and other leaders. Below is this month's puzzle contest; the solution will be published in a future issue. The winners will receive a free copy of *How to Ace the Brainteaser Job Interview* (McGraw-Hill) signed by the author and *Registered Rep.* contributing editor, John Kador.

### THIS MONTH'S CONTEST

**Alex is a stockbroker.** He has a quota of 800 trades per day or 4,000 trades per week. He can transact 100 trades every hour, or 800 trades in a typical eight-hour day. After 40 hours, Alex meets his quota. But when he doesn't get a year-end bonus, Alex decides to go on a slow-down strike.

When he comes in to work on Monday morning, Alex does 99 trades the first hour, but only 98 trades the second hour, 97 trades the third hour, and 96 trades the hour after that, and so on, until the 99th hour, when he does but one trade.

**How long will it take for Alex to meet his weekly quota of 4,000 trades?**

A) About 45 hours

B) About 56 hours

C) About 67 hours

D) About 80 hours

E) He will never meet the quota

### BRAINTEASER #2: IN THE VAULT

**Question:** A bank had three vaults: one for gold, one for silver and one for platinum. A different guard protected each vault. Gus guarded the gold vault; Sylvester guarded the silver vault; Plato guarded the platinum vault. The bank president had a problem: He knew the bank's three vaults together had 12,000 bars, but he didn't know how many of each type there were. The guards, unfortunately, were not cooperative. The best that the bank president could get was just one statement from each of the guards.

Gus: There are 3,000 silver and 5,000 platinum bars.

Sylvester: There are 3,000 gold and 5,000 platinum bars.

Plato: There are 4,000 gold and 3,000 silver bars.

Unfortunately, only one of the guards was telling the truth. The statements of the other two guards were incorrect in at least one amount.

**Question:** If there are 12,000 metal bars in total, how many of each type are there?

**Solution:** We know there are a total of 12,000 bars. Let's assume each of the statements to be true in turn and examine the consequences. If Gus is telling the truth, there are 3,000 silver bars, 5,000 platinum bars and, hence, 4,000 gold bars. However, this would make Plato's statement also true. Since only one guard's statement can be true, Gus's statement cannot be valid. By the same reasoning, if Plato is truthful, so is Gus. So Plato's statement cannot be true. Only if Sylvester is telling the truth are the other statements false. Sylvester is the truthful guard.

**Answer:** There are 3,000 gold bars, 4,000 silver bars and 5,000 platinum bars.

**Please email your solution to** John Churchill at [email protected], using the subject line, “April 2007 Puzzler.” Deadline is May 8, 2007. We will select three winners from all correct entries. Extra consideration will be given to offbeat or elegant solutions. Winners will receive a signed copy of John Kador's *How to Ace the Brainteaser Job Interview*. Good luck.

### Winners of the Previous Puzzler

*The previous contest presented 10 related words and phrases all jumbled up.*

- RAWEST MORTALS
- BLOOM XENIX
- A MERGER LOTS NO
- DOT FROM OR
- ALLERGENIC ERECT
- HOAXER CONVECT
- PINCH COIL SLOOP
- COURT PIG I
- NOT ALIENATING NICER PARAMOUR
- HIS BAN IS ON ANCIENT TERMINALS USE

- Walmart Stores
- Exxon Mobil
- General Motors
- Ford Motor
- General Electric
- Chevron Texaco
- Conoco Phillips
- Citigroup
- American International Group
- International Business Machines

The challenge was to unjumble them.

Solution: These are the 10 largest U.S. companies on the Fortune 500 (2006).

Congratulations to the winners:

Paul Stratton, Edward Jones Investments, Denver

Scott Kreger, Ferris Baker Watts, Rockville, Md.