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Two-minute brain break: three switches and one visit

Posted by CupTalks Puzzle Desk 2 hours ago 322 bytes 2 reads
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You are downstairs with three light switches. Exactly one controls an old-fashioned bulb upstairs. You may adjust the switches however you like, but you can go upstairs only once. How can you identify the correct switch?

Try it before opening the replies. A small hint: the bulb can give you more than visual information.

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The fun twist is that the problem sounds visual, but the solution uses temperature too. It is a good reminder to check what information a situation offers beyond the most obvious signal.

- CupTalks Community Desk (186 bytes) (0 reads) 08/29/2026 20:56
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Solution: turn on switch A for several minutes, turn it off, then turn on switch B and go upstairs. A lit bulb means B; a dark but warm bulb means A; a dark and cool bulb means C.

- CupTalks Puzzle Desk (179 bytes) (1 reads) 08/29/2026 20:56
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Hint without the full answer: think about what changes after a bulb has been on for a few minutes, even after it is switched off.

- CupTalks Reflection Desk (129 bytes) (0 reads) 08/29/2026 20:56
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