The Puzzler #8

Apr 1, 2008 12:00 PM, BY JOHN KADOR

             

THIS MONTH'S CONTEST

BRAINTEASER: TRAPPED IN A BLENDER

Google currently favors this puzzle in its interviews. There is no right or wrong answer. The interviewer is looking for agility of mind and playful creativity, as well as some rigor in approaching the problem. In other words, it's a real test. (I hear Google interviewers don't like candidates to treat it like a joke.)

MORE BRAINTEASERS CURRENTLY MAKING THE ROUNDS

1. TRAINSPOTTING

   A man who enjoys watching trains takes walks at random times during the day to a nearby train crossing, and waits for a train to go by. Once he's seen a train he leaves the station. As he walks home, he makes a note of whether he saw a freight train or a passenger train. Over 20 years, his figures shows that 90 percent of the trains he's seen pass by have been passenger trains. He decides to see if his figures coincide with statistics listed on the railroad's website. He is startled to learn that the number of passenger trains and freight trains running on that track per hour have always been precisely equal. How is it possible that the man saw such a disproportionate number of passenger trains?

2. FIND THE PRODUCT

   Find the product of the following series: (x-a) (x-b) (x-c) … (x-z)

3. WHICH IS THE MAGNET?

   You are in a room where there are no metal objects except for two iron rods identical in appearance. One of the roads is magnetized; the other is not. How can you identify which rod is the magnet?

4. LILY PADS EVERYWHERE

   A lily pad doubles in size every day. If it takes 60 days for 100 percent of a pond to be covered with lily pads, on what day is 50 percent of the pond covered?

5. WEIGHT ON MOON AND EARTH

   What weighs more on the moon than on the earth?

SOLUTIONS FOR PUZZLES 1-5 MAY BE FOUND ON REGISTERED REP'S WEB SITE [HTTP://REGISTEREDREP.COM/ADVISORLAND/LEISURE/0408_BRAINTEASER]

Please email your solution to this month's contest to jkador@jkador.com by May 15, using the subject line, “Blender Puzzler.” We will select two winners from all correct entries, with extra consideration given to offbeat or elegant solutions. Winners will receive a signed copy of How to Ace the Brainteaser Job Interview (McGraw-Hill), signed by the author and Registered Rep. Contributing Editor John Kador.

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