There are twelve wires that run from your cellar to your roof. Unfortunately on their journey they could be randomly mixed up, so you can't tell which cellar wire-end corresponds to which roof wire-end. You have a battery and a light bulb, and you can temporarily twist wires together. You can also travel from the cellar to the roof and back again any number of times. Thus you can construct circuits and test the wires at either end in order to deduce what is going on. But it’s a long way to the roof. So, starting at the bottom, what is the minimum number of journeys you have to make, in order to work out exactly which wire-end in the cellar corresponds with which wire-end on the roof?

Although this is a good problem, it is assuming that we are living in a weird Survivor like world, where we can't just take a trip to the store and buy a few different colored lightbulbs and a video camera linked to a laptop.  Then, hook all of the different colored lightbulbs to each wire, set up the camera to look at them, go to the attic with the battery and laptop.  Connect each line to the battery and watch to see which lights up which bulb and label accordingly.  Then you know which end goes to what.  :)  And, most people these days have lightbulbs and laptops and video cameras.  Just put a little coloring on the clear light bulbs you already have, thus saving the trip to the store as well.

But, alas, we only have one light bulb and a battery, so I'll leave it to the others.  They've done a good job with solutions so far.  :)

Posted by Renee on 2004-07-01 10:00:37