You are in the first room of a two-room apartment. There
are three individual switches each connected to a bulb,which are in the second room. The rooms are
separated by a door that is closed, so you cannot see the bulb. You are allowed to turn each switch on and off and
enter the second room only once. How will you determine which switch is
connected to which bulb.
Obviously there is no sense to turn on all 3 switches.The idea is that nobody said that we might
only look at the lights.For instance we can
touch them. The matter is that if the bulb was on the light
for a long time but then was turned out, it continues
to be HOT for a certain time in contrast to the bulb that
has not been on the light at all! From here we get the
following solution. First you have to turn on one of the
switches (say switch 1) and wait for a certain time . Then you have to turn this switch off and turn
on another one (switch 2). After that you enter the
room and see what bulb is on the light. It is clear that it
corresponds to switch 2. Then you touch the other
bulbs. The one that is warm corresponds to switch 1
while the last one is corresponds to the 3rd switch.
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