April 2008 Brainteaser Solutions

1. Trainspotting Freight trains were always scheduled to come six minutes after passenger trains. That means that 54 out of every 60 minutes, the man would arrive at the station, wait for a passenger train and then leave. There are only six minutes per hour, however, when he would arrive having missed the passenger train, and would wait to encounter a freight train. Thus probability dictates that the man&#8217;s odds of arriving after a freight train, and before a passenger train, are 54:6 or 9:1, or 90 percent. 1. Trainspotting Freight trains were always scheduled to come six minutes after passenger trains. That means that 54 out of every 60 minutes, the man would arrive at the station, wait for a passenger train and then leave. There are only six minutes per hour, however, when he would arrive having missed the passenger train, and would wait to encounter a freight train. Thus probability dictates that the man&#8217;s odds of arriving after a freight train, and before a passenger train, are 54:6 or 9:1, or 90 percent.

1. Trainspotting
Freight trains were always scheduled to come six minutes after passenger trains. That means that 54 out of every 60 minutes, the man would arrive at the station, wait for a passenger train and then leave. There are only six minutes per hour, however, when he would arrive having missed the passenger train, and would wait to encounter a freight train. Thus probability dictates that the man’s odds of arriving after a freight train, and before a passenger train, are 54:6 or 9:1, or 90 percent.

2. Find The Product
Zero. Whenever you are presented with an equation of such apparent complexity as (x-a) (x-b) (x-c) … (x-z), you must know that something is hidden. Indeed it is, and the solution is hidden in the ellipses. What’s hidden in those not-so harmless little dots? If you fill in the missing elements, you will eventually come to (x-x). Because (x-x) is zero, the rest of the series, no matter how tangled, is zero.

3. Which Is The Magnet?
Put the end of one metal rod (let’s call it rod A) perpendicular to the center of the other (rod B). Bar magnets are active at their poles or ends, but not at their centers (where the forces of the two poles cancel each other out). So, if the magnet is rod A, there will be a definite magnetic attraction. If the magnet is rod B, there will be no attraction.

The 59th day.

6. Weight On Moon And Earth
Any balloon filled with a gas that is lighter than air, such as helium or hydrogen. That’s the literal solution. There is a metaphorical solution as well: What weighs more on the moon than on the earth? The conscience of an astronaut—if the astronaut left for the moon on his wedding anniversary and he or she forgot to get flowers for his or her spouse.