Brain Teasers at Job Inteviews

20 Sep

The economy still isn’t robust, so companies are thinking of new ways to torture hapless job applicants.  Often they’ll use some kind of brain teaser which is supposed to gauge your ability to think. This is pure nonsense of course, but they do it anyway ’cause 1.) They’re sadistic and 2.) Some of ’em are dumb enough to think that this proves anything.

In my humble opinion, it’d make more sense to measure the candidate’s work ethic, honesty, and dependability, but that’s not what they do.  Here’s one that they might throw at you, so be prepared. It’s not too difficult, unless you’re dealing  with the added stress of a job interview.

You are in a room that has a light switch panel with 3 switches, only one of which turns on a light (the other two don’t do anything.)  The light in question is in the room next door, and it is at a height where you are able to touch it. You can remain in the room with the light switches as long as you like, but once you go into the room with the light, you cannot return to the room where the switches are.  You have to determine which switch turns on the light. How do you do this?

Now, you’ve probably already surmised that this problem would be a lot simpler if you had only two switches to consider.  You’re right! Try to think about this for a bit before reading on (unless you’re really impatient, like me.)


Answer: Let’s number the switches 1, 2, 3.

  • Turn on Switch 1.
  • Wait a few minutes (5 minutes would probably be more than adequate.)
  • Turn off Switch 1.
  • Turn on Switch 2.
  • Enter the room where the light is.
  • If the light is on, Switch 2 is the wired switch.  If the light is off, but the bulb is warm, Switch 1 is the wired switch.  If the light is off, and the bulb is cool, then Switch 3 is the wired switch.

Another solution would be to remove the switch plate with a screwdriver and examine the wiring, but that isn’t the answer they’re going for.

One more thing: if they do throw this one at you, a little acting will go a long way.  Before you answer, hesitate and act like what they’ve asked you is the hardest problem you’ve ever encountered.


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