# You are standing outside a closed door. On the other side of the door is a room that has...........Solve this Puzzle?

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You are standing outside a closed door. On the other side of the door is a room that has three light bulbs in it. The room is completely sealed off from the outside. It has no windows and nothing can get in or out except through the door. On the outside of the room there are three light switches that control each of the respective light bulbs on the other side of the door.

Your assignment is to determine which light switch controls which light bulb. You are allowed to enter the room only once, and once you come out, you must be able to state with 100% certainty which light switch controls which light bulb.

posted Mar 28, 2017

+1 vote

Incandescent bulbs have a tendency of becoming hotter with time which can be used to determine which switch belongs to which.
Step 1: Switch 1 bulb on and wait for 15 minutes.
Step 2: Switch that bulb off and switch any 1 of the other 2 bulbs.
Step 3: Immediately enter the room after step 2 and touch the 2 unlit bulbs.

Conclusions:
The bulb that glows on entering is the one that belongs to the switch that you turned on just before entering.
The hotter of the 2 unlit bulbs is the one that belongs to the switch that remained on for 15 minutes and the other bulb is simply belonging to the remaining untouched switch.

Put on one switch - say switch A
Put on another switch for some time and thrn sitch it off - say switch B
Keep the other switch off - say switch C

Get into the room

Switch A controls the bulb that is alight.
Touch the other two bulbs to see which is warm. Swich B controls that bulb.
Swich C controls the remaining bulb.

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