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100 Lights and 100 Switches (Posted on 2022-11-28) Difficulty: 3 of 5
• There are precisely 100 lights in a huge room.
• A switch panel outside the room has 100 switches each corresponding to one light in the room.
• None of the switches or lights are labeled, so its extremely difficult to identify which switches turns on which light.
• Stan is standing outside of the room and his task is to map each switch to its corresponding light using a marker pen.
• He has to accomplish this mapping in a minimum number of trips to the room.
• Initially all the lights are turned off.

Determine the minimum number of times Stan needs to enter the room to complete the mapping of each switch to its corresponding light.

• To check the state of a light Stan must enter the room. He cannot check it from outside.
• There is nothing related to the heating of a light.

See The Solution Submitted by K Sengupta    
Rating: 5.0000 (1 votes)

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Some Thoughts Guess number by cards Comment 6 of 6 |
I am reminded of a trick where an assortment of numbers are written on seven cards.  The subject is to choose a number between 1 and 127, and then hand the puzzler every card where that number appears.  From the cards, the puzzler is quickly able to guess the number.

The first card has all odd numbers from 1 to 127.  The second has 2, 6, 10, 14, etc.  The third has 4, 12, 20, etc.  And so on.  The puzzler simply adds the first number on each card together to determine the subject's number.

If any number between 1 and 100 can be determined in this fashion with 7 cards, then it will work for the lightbulb room as well.

  Posted by hoodat on 2022-12-23 13:17:46
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