Question

In your cellar there are three light switches in the off position. each switch controls one of three light bulbs on floor above. you may move any of the switches but you may only go upstairs to inspect the bulbs. when upstairs, you cannot access the switches. what is the minimum number of times you need to go upstairs to determine the switch for each bulb?

Answer 1

You have a set of 3 light switches outside a closed door. One of them controls the light inside the room. With the door closed from outside the room, you can turn the light switches on ...