Light Switch

Here’s a logic puzzle for your amusement:

You live on the top floor of a highrise. On your desk sits a lamp which is currently off. The lamp has no integral switch. Instead, it is conveniently controlled by a switch in the sub-basement (the architect of the building won an award for creative, ‘green’ building design by placing all of the light switches in the sub-basement to reduce extravagant and wasteful wiring. You may take comfort that the architect also lives in the building, which curiously maintains a box of rotting tomatoes near his apartment door).

Further complicating your life, the light switch is one of three, with the other two switches not connected to anything (the electrician got a deal on salvaged light switches from Botswana). All of the switches are off.

Your task is simple: determine which of the three switches controls the lamp.

Oh, did I mention you are malnourished and only have enough energy to make the trip down to the sub-basement one time (the contractor ‘forgot’ to build the elevator and is currently living like a king in a cardboard box under a bridge. It’s a single-storey box.)

You may go downstairs one time, flip the switches up and down as much as you like, take a nap, or play fetch with the rats, and when you finally arrive back at your apartment, gasping, you must determine which of the three switches controls your lamp. Easy.

You may not use trickery. No tools, voltage meters, cameras, mirrors, trained seals, telephones to talk with someone in your apartment, etc. Just you, the switches, and the lamp.


Here’s the solution.

I Switch Which Switch?

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