The Grey Labyrinth is a collection of puzzles, riddles, mind games, paradoxes and other intellectually challenging diversions. Related topics: puzzle games, logic puzzles, lateral thinking puzzles, philosophy, mind benders, brain teasers, word problems, conundrums, 3d puzzles, spatial reasoning, intelligence tests, mathematical diversions, paradoxes, physics problems, reasoning, math, science.


The Lighting Round



It’s the end of another GL competition and you are led into the memorable room where Paladin had his Grey Labyrinth Semaphore clocks. However, this time, the shelf is clean and a pile of lighting equipment is on the floor. A note hangs from the shelf saying “sorry, but I spilled coffee on the shelf and in cleaning it up I completely ruined your light display, so I just disassembled it and left it on the floor” Signed, Skinny. Great you think, it took you a lot of time to setup a nice display message here for the GL competition. Looking at the pile, you realize this can be the final puzzle and ask the contestants if they can put it back the way it was meant to be.

On the floor are an assortment of 3x3 LED boards used for lighting any combination of the 9 bulbs by tying them together with a connector. Meaning that all bulbs are in an off state unless a connector is placed between two of them. The bulbs are 2 inches apart in width and height.

There are 43 connectors of length 2 inches, 6 connectors of a length around 2.8 inches, and 1 connector just under 4.5 inches.  Also, there are 8 LED boards in all. Picking up the boards in no specific order, you find the following information written on the back of them. Note, that on most of these there is no indication of which side is up, so the numbering of the nine bulbs is arbitrary and it may need to be turned to face another way.

1 - Only info is that bulbs 1,2,3,4,6,7,8,9 are ON
2 - Only info is that bulbs 3,4,5,6,9 are ON
3 - Only info is that bulbs 1,2,3,4,5,7,8,9 are ON
4 - Labeled this side up, and bulbs 1,3,4,5,6,7,9 are ON
5 - Labeled this side up, and bulbs 1,2,3,5,7,8,9 are ON
6 - Only info is that bulbs 1,3,4,5,6,8 are ON
7 - Only info is that bulbs 1,2,3,6,7,8,9 are ON
8 - Labeled this side up, and bulbs 1,3,4,5,6,7,9 are ON

You start to say that you don’t know if they can be reassembled without making an assumption, but on the floor you notice labels that were numbered 1 through 8 which used to tell the correct order the boards were placed in. It’s a shame they fell off. But, you only notice seven of them.  As you pick up the boards again, a label marked #1 falls off of a board and lands on the board you temporarily called #3. Unfortunately you are unsure which board it fell off of. Thinking it over, and looking at the label, you exclaim, “Well if you can tell me what the problem was, I’m sure you can now tell me the correct answer as well.”


Image by Courk.


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