Can you solve the 3-switches problem?


#1

[Read the post]


#2

Unscrew the cover plates and wire them all together in series.

Also, that impossible knot that Gordon won’t shut up about? Just cut it in half with your sword.


#3

Sounds like a hot problem.


#4

Yup, obviously you’ve got it.


#5

Wouldn’t the real puzzle be either why somebody put the switches there? Or why I can only go to the attic once?

I suppose I would look to see what else in the house was controlled by them, this by elimination would suggest which controlled the lamp in the attic. Then I would finally go up there. Assuming of course that whatever joker wired these actually connected all three switches to anything! Otherwise I’d switch them all on.


#6

How do you do it?

You do nothing to the first switch.
You flick the second switch on and off once.
You flick the third switch on and off a hundred times.
You go up to the attic and ask Grandpa how much lightning there’s been this afternoon.


#7

Eccentric millionaire, burying Lincoln’s gold.

Bears. They’re attracted to the light.


#8

This puzzle will become obsolete as soon as we all use Light rahter than Heat-Bulbs.


#9

But what if they’d been upgraded to LEDs?


#10

Flip one switch on. Wait 10 minutes. Flip switch off. Switch another switch on. Go upstairs. If it’s on, it’s the last switch. If it’s off, touch the bulb. If it’s warm, it’s the first switch. If it’s cold, it the switch you never touched. Even works with LED bulbs and fluorescent, as you touch the electronics bits instead.


#11

Damn, tried this in my house. All LED lighting. Didn’t work.

Next you’re going to be telling me a puzzle about my rotary telephone!

Edit: Tried to touch the electrical connections instead as @Chipsa suggested, but now I have electrocuted myself to death. Hmmm… Cavete solver.


#12

so after thinking about it a minute, i guess the solution has something to do with ohm’s law and the conservation of energy.

however, nowadays with these LED and compact fluorescent bulbs, i think it would be hard to detect the 100mA or so that these bulbs pull. things are probably different with a real 100W incandescent bulb.


#13

Turn the first one on and leave it on for several minutes… 5 should do it. Then turn it off and turn on the second one. Then go upstairs. If it’s off and hot, it was the first. If it’s on, it was the second. If it’s off and cold it’s the third.


#14

http://the-toast.net/2015/02/12/tell-logic-puzzle/


#15

I would just turn on all the switches and be satisfied there is a light on in the attic.


#16

Tie a long piece of string to each of the light switches, go up to the loft with the strings and use them to turn the lights on from up there.

Or that warm thing, whatever.


#17

A point covered by the article, actually. You just have to leave it on a bit longer, and pay closer attention to the temperature. (LED’s do get warm, just not as warm, as quickly)


#18

Easy- flip the first switch on for an extended duration. Next, flip the first switch off and flip the second switch on. Run up the stairs. If the bulb is warm but not lit, the first switch turns it on. If the bulb is lit, it’s the second switch. Of the bulb is off and cold, the third switch is the one that turns the light on and off.

Thanks to my 8th grade math teachers, Herr Hauck and Herr Cutter, for this


#19

eff it… I’d probably just call an electrician


#20

I guess it relies on the assumption that leaving one of the lights on will cause that light to heat up, and that upon visiting the attic you can detect this (light is accessible for inspection, light does not cool rapidly, etc etc etc).

Unless the attic is particularly well shielded to prevent comms links, popping up to open a Skype connection seems to be the most straightforward answer.

If you wait until dark and switch off your other lights, it might be possible to do it with no visits, if for example, the attic light provides a degree of illumination over a location visible from the switches.