On Friday we posed a nice easy puzzle that has been around for a while. Well at least as long as electric lights!
There are three light bulbs in the attic and three light switches downstairs, out of sight of the attic. Each light switch operates one, and only one, light bulb. And all the light bulbs are currently switched off.
The problem is to identify which light switch is connected to which light bulb.
You can switch the light switches on and off as many times as you want, but you can make only one trip to the attic.
The solution is to turn on light switch A for ten minutes or so. Then turn it off an turn on light switch B. And go to the attic . . .
The light bulb that is lit is connected to light switch B. The light bulb that is warm is connected to light switch A. And the other light bulb is connected to light switch C.
Notwithstanding that low-energy light bulbs don't get as warm as the old ones!