2007-05-07

Lights and switches

Here's another of my favorite puzzles:

You have three switches connected to three bulbs. The switches and bulbs are in different rooms. You can't see the bulbs from the switch room and vice-versa.

Your task: adjust the switches and then make a single visit to the bulb room to determine which switch is connected to which bulb. You can't revisit the switch room after you leave it.

5 comments:

Mark Hanington said...

This puzzle would be more gripping if electric chairs were somehow involved.

Mark Hanington said...

All bulbs are in one room, all switches are another one room, - right? And all switches have a idication that they are either on or off. Is that right?

fiona-h said...

yes

Anonymous said...

Turn one of the switches on. Stand there and wait for 15 minutes. Then turn on a second switch. One minute later, turn both switches off and run into the bulb room and check temperatures. First switch is hottest bulb, second switch is less hot, third switch is a cold bulb. (Hopefully, you can reach the bulbs. Also, it'll be dark in there so be careful.)

fiona-h said...

good! you can do this another way too: turn 2 on. Wait 5 min. Then turn only 1 off. Go into the other room. One is on, one is off and hot, and the third is off and cold.