Post:
You have three switches in one room and a single light bulb in another room. You are allowed to visit the room with the light bulb only once. How do you figure out which switch controls the bulb? Write your answer in the comments before looking at other answers.
Comment:
If this were an interview question, the correct response would be "Do you have any relevant questions for me? Because have a long list of things that more deserving of my precious time than to think about this!
The official answer to this riddle is turn switch 1 on for a minute or so, switch it off then switch 2 on. if the bulb is hot but dark, its 1, if it’s lit it’s 2 and if it’s out and cold its 3.
the adult answer is why do I have only one chance to walk in the room?
8 lightswitch states. Smack em all on, and smack em all off. If there’s no change, that’s a bad lightswitch
this is the classic answer but it also fails pure logic because the question only implies one of them actually works, and even then, it’s only one of them. the truth is any number of them could work, or a specific combination, or a number of combinations, or it might be none. the bulb itself to could be busted. my point is not to be an uncooperative asshole but that a logic puzzle that relies on real world properties should cover its bases.
if hot they’re using out of date lighting, who the fuck uses incandescent bulbs this far into the 21st century? they have failed their interview with me.
LED do not have a 100% efficiency, and do produce waste heat. A lot less than an incandescence one, sure, but enough for that answer to be valid.
Well, maybe you’d better wait 10min instead of one, to make sure the led lightbulb heats enough, but still…
note the premise specifies HOT.
none of my LED bulbs get hot even after hours. they do warm up from ‘cold’ but HOT?
ymmv.
The “premise” is detecting that a now dark light was recently turned on by feeling for residual heat. “Hot” is a relative term.
The question is outdated as fuck too. It’s not a new riddle.
You know, we’re talking about how pointless a riddle it is. “Why can’t I walk into the room more than once?” I’ve heard similar hiring riddles about things like “You’ve got ten ethernet cables that run the length of a long hallway. They’re not marked at either end, what’s the most efficient way of finding out which is which?”
And you know what? If I’m hiring a networking guy, I don’t want him to deliver me an “ooh I know this one” answer to that, I want him to tell me he’s got a cable tester with several remote probes so he can figure that out in a small number of trips. Maybe show me how he can hook a couple together with a coupler and use the cable length function to shave a couple of trips off. Not recite a memorized brain teaser answer.