Brain Teaser

DeerKing · Apr 11, 2003

Here's an easy one to start you out....
You're a contractor working on renovating a 10 story building. You observe three light switches on the ground floor that correspond to three light bulbs on the 10th floor. No wiring diagrams are available and you can't see the lights from the ground floor. The elevator is out of commission so you don't want to make more than one trip up the stairs to check the lights. How do you accurately determine which switch goes with which light bulb, while only making one trip up the stairs?

_droptine_ · Apr 11, 2003

Ok,
Here is how I would do it.

1) Turn on two of the light switches.
2) Go up to the 10th story, the light that is not on corresponds to the switch that you did not turn on.
3) Take out one of the lightbulbs that is on, then go back downstairs.
4) Downstairs at the light switches, one at a time, connect the light back into the circuits of the two switches you turned on.
5) The circuit that lights the light will be to the light bulb you turned on and left on. The circuit that won't light the light will be to the one where you removed the bulb.

dutch · Apr 11, 2003

EASY ONE?!

DeerKing · Apr 11, 2003

Drop
Your making it to complex. There is a much easier way without rewiring or unscrewing lightbulbs.....

_droptine_ · Apr 11, 2003

What do you expect? I am an engineer. We like to make things more complex than they need to be.

I looked up the answer to this and I had been totally going down the wrong track.

alwayzbhuntin · Apr 11, 2003

You take a phone with you and have someone else on the ground floor throwing the switches...thats what I would do.

glockmister · Apr 11, 2003

the light switch on the north side of the building turns on the light on the northe side

the light switch in the middle turns on the one in the middle

and the light swith on the south side of the building turns on the light on the south side

or same thing east and west

kidneystone · Apr 11, 2003

Switch on #1 and let it stay on for ten minutes. Switch off #1 and switch on #2. Go upstairs. The lighted bulb goes with switch #2. Feel the other two bulbs. The "hot" bulb goes with #1. The cold bulb goes with #3.