Brainteaser Answer 11:
First and foremost, for your own reference, name the switches “a, b and c.”
Turn on switches a and b.
- Wait 10 minutes.
- Turn switch b off.
- Enter the room.
- Whichever light bulb is now on, is controlled by switch a (the only one, still on).
- Feel the other 2 light bulbs (carefully).
- Whichever light bulb is warm is controlled by switch b.
- The cold light bulb must be controlled by switch c.
All you have to do is think outside the box!