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The Three Switches

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  • D dandy72

    Do you know, before you start flipping switches, whether the light is already on?

    J Offline
    J Offline
    Jorgen Andersson
    wrote on last edited by
    #7

    Well spotted.

    Wrong is evil and must be defeated. - Jeff Ello

    1 Reply Last reply
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    • OriginalGriffO OriginalGriff

      Wouldn't work in this house: some of the switches are "top for off", others are "bottom for off"...:sigh: One of these days I'll sort it out, but I'm afraid the writing won't take changes and I don't want to have to redecorate... :laugh:

      Bad command or file name. Bad, bad command! Sit! Stay! Staaaay...

      J Offline
      J Offline
      Jorgen Andersson
      wrote on last edited by
      #8

      Well, he didn't state top or bottom, he stated off. :)

      Wrong is evil and must be defeated. - Jeff Ello

      OriginalGriffO 1 Reply Last reply
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      • OriginalGriffO OriginalGriff

        Two ways I can think of: 1) Look at the effect of each switch on other lights in the house. The one that doesn't have any effect is the attic one (or a bulb is blown) 2) Send the wife up to the attic and tell her to yell when the light goes on!

        Bad command or file name. Bad, bad command! Sit! Stay! Staaaay...

        J Offline
        J Offline
        Jorgen Andersson
        wrote on last edited by
        #9

        Those are practical solutions, not adjusted for silly puzzles. My wife wouldn't go up to the attic in any case.

        Wrong is evil and must be defeated. - Jeff Ello

        OriginalGriffO _ 2 Replies Last reply
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        • J Jorgen Andersson

          Those are practical solutions, not adjusted for silly puzzles. My wife wouldn't go up to the attic in any case.

          Wrong is evil and must be defeated. - Jeff Ello

          OriginalGriffO Offline
          OriginalGriffO Offline
          OriginalGriff
          wrote on last edited by
          #10

          I'm a practical person! :laugh:

          Jörgen Andersson wrote:

          My wife wouldn't go up to the attic in any case.

          Too many spiders? (Can't stand the venomous little buggers, myself)

          Bad command or file name. Bad, bad command! Sit! Stay! Staaaay...

          "I have no idea what I did, but I'm taking full credit for it." - ThisOldTony
          "Common sense is so rare these days, it should be classified as a super power" - Random T-shirt

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          • J Jorgen Andersson

            Well, he didn't state top or bottom, he stated off. :)

            Wrong is evil and must be defeated. - Jeff Ello

            OriginalGriffO Offline
            OriginalGriffO Offline
            OriginalGriff
            wrote on last edited by
            #11

            If you don't know what they control, you don't know which way is on... ;)

            Bad command or file name. Bad, bad command! Sit! Stay! Staaaay...

            "I have no idea what I did, but I'm taking full credit for it." - ThisOldTony
            "Common sense is so rare these days, it should be classified as a super power" - Random T-shirt

            J 1 Reply Last reply
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            • OriginalGriffO OriginalGriff

              I'm a practical person! :laugh:

              Jörgen Andersson wrote:

              My wife wouldn't go up to the attic in any case.

              Too many spiders? (Can't stand the venomous little buggers, myself)

              Bad command or file name. Bad, bad command! Sit! Stay! Staaaay...

              J Offline
              J Offline
              Jorgen Andersson
              wrote on last edited by
              #12

              Mice traps, or rather the reason for them.

              Wrong is evil and must be defeated. - Jeff Ello

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              • OriginalGriffO OriginalGriff

                If you don't know what they control, you don't know which way is on... ;)

                Bad command or file name. Bad, bad command! Sit! Stay! Staaaay...

                J Offline
                J Offline
                Jorgen Andersson
                wrote on last edited by
                #13

                OriginalGriff wrote:

                If you don't know what they control, you don't know which way is on

                So if you know that they control a lamp in the attic... :doh:

                Wrong is evil and must be defeated. - Jeff Ello

                1 Reply Last reply
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                • J Jorgen Andersson

                  Downstairs in a house are three identical on-off switches. One of them controls the lamp in the attic. The puzzle is to work out which switch controls the lamp. The rules are as follows. You are allowed to manipulate the switches all you like, and then you are allowed a single trip to the attic. How do you do it? To clarify: When you are downstairs there is no way to see into the attic, or see reflected light from the attic. Once you have gone to the attic you are not allowed back to the switches. <edit>you can also assume original state of all switches to be off.</edit><hint>Otherwise it won't work</hint> Note: If you already know the answer, or reads the newspaper where I nicked the puzzle from, then please don’t write it up immediately in the comments! Give those who have never heard it before a chance to suffer, I mean enjoy finding the solution.

                  Wrong is evil and must be defeated. - Jeff Ello

                  Richard Andrew x64R Offline
                  Richard Andrew x64R Offline
                  Richard Andrew x64
                  wrote on last edited by
                  #14

                  What's the purpose of going to the attic if you cannot go back to the switches afterward?

                  The difficult we do right away... ...the impossible takes slightly longer.

                  1 Reply Last reply
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                  • J Jorgen Andersson

                    Downstairs in a house are three identical on-off switches. One of them controls the lamp in the attic. The puzzle is to work out which switch controls the lamp. The rules are as follows. You are allowed to manipulate the switches all you like, and then you are allowed a single trip to the attic. How do you do it? To clarify: When you are downstairs there is no way to see into the attic, or see reflected light from the attic. Once you have gone to the attic you are not allowed back to the switches. <edit>you can also assume original state of all switches to be off.</edit><hint>Otherwise it won't work</hint> Note: If you already know the answer, or reads the newspaper where I nicked the puzzle from, then please don’t write it up immediately in the comments! Give those who have never heard it before a chance to suffer, I mean enjoy finding the solution.

                    Wrong is evil and must be defeated. - Jeff Ello

                    R Offline
                    R Offline
                    R Giskard Reventlov
                    wrote on last edited by
                    #15

                    I send a drone to the attic with a camera so I can see which switch switches the light on.

                    1 Reply Last reply
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                    • J Jorgen Andersson

                      Downstairs in a house are three identical on-off switches. One of them controls the lamp in the attic. The puzzle is to work out which switch controls the lamp. The rules are as follows. You are allowed to manipulate the switches all you like, and then you are allowed a single trip to the attic. How do you do it? To clarify: When you are downstairs there is no way to see into the attic, or see reflected light from the attic. Once you have gone to the attic you are not allowed back to the switches. <edit>you can also assume original state of all switches to be off.</edit><hint>Otherwise it won't work</hint> Note: If you already know the answer, or reads the newspaper where I nicked the puzzle from, then please don’t write it up immediately in the comments! Give those who have never heard it before a chance to suffer, I mean enjoy finding the solution.

                      Wrong is evil and must be defeated. - Jeff Ello

                      P Offline
                      P Offline
                      Peter_in_2780
                      wrote on last edited by
                      #16

                      The classic solution (which I won't give away) may not work too well with modern LED globes! CFLs maybe. Cheers, Peter

                      Software rusts. Simon Stephenson, ca 1994. So does this signature. me, 2012

                      R G D S I 6 Replies Last reply
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                      • J Jorgen Andersson

                        Downstairs in a house are three identical on-off switches. One of them controls the lamp in the attic. The puzzle is to work out which switch controls the lamp. The rules are as follows. You are allowed to manipulate the switches all you like, and then you are allowed a single trip to the attic. How do you do it? To clarify: When you are downstairs there is no way to see into the attic, or see reflected light from the attic. Once you have gone to the attic you are not allowed back to the switches. <edit>you can also assume original state of all switches to be off.</edit><hint>Otherwise it won't work</hint> Note: If you already know the answer, or reads the newspaper where I nicked the puzzle from, then please don’t write it up immediately in the comments! Give those who have never heard it before a chance to suffer, I mean enjoy finding the solution.

                        Wrong is evil and must be defeated. - Jeff Ello

                        M Offline
                        M Offline
                        Member 11762424
                        wrote on last edited by
                        #17

                        if the light is incandescent or halogen, it will get hot if left on. so switch on the first switch, and get distracted for 10 minutes, switch it off, switch on the next one and race upstairs. If the light is on, it is that 2nd switch. If it is off but hot, it was the first switch. Else it is the third switch. If it's an energy-efficient bulb, this won't work.

                        J M 2 Replies Last reply
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                        • OriginalGriffO OriginalGriff

                          Two ways I can think of: 1) Look at the effect of each switch on other lights in the house. The one that doesn't have any effect is the attic one (or a bulb is blown) 2) Send the wife up to the attic and tell her to yell when the light goes on!

                          Bad command or file name. Bad, bad command! Sit! Stay! Staaaay...

                          J Offline
                          J Offline
                          JimmyRopes
                          wrote on last edited by
                          #18

                          OriginalGriff wrote:

                          Send the wife up to the attic and tell her to yell when the light goes on!

                          :thumbsup:

                          Once you lose your pride the rest is easy. In the end, only three things matter: how much you loved, how gently you lived, and how gracefully you let go of things not meant for you. – Buddha

                          1 Reply Last reply
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                          • J Jorgen Andersson

                            Those are practical solutions, not adjusted for silly puzzles. My wife wouldn't go up to the attic in any case.

                            Wrong is evil and must be defeated. - Jeff Ello

                            _ Offline
                            _ Offline
                            _Asif_
                            wrote on last edited by
                            #19

                            Yup, same goes to my wife, she wont do it in any case :)

                            1 Reply Last reply
                            0
                            • J Jorgen Andersson

                              Downstairs in a house are three identical on-off switches. One of them controls the lamp in the attic. The puzzle is to work out which switch controls the lamp. The rules are as follows. You are allowed to manipulate the switches all you like, and then you are allowed a single trip to the attic. How do you do it? To clarify: When you are downstairs there is no way to see into the attic, or see reflected light from the attic. Once you have gone to the attic you are not allowed back to the switches. <edit>you can also assume original state of all switches to be off.</edit><hint>Otherwise it won't work</hint> Note: If you already know the answer, or reads the newspaper where I nicked the puzzle from, then please don’t write it up immediately in the comments! Give those who have never heard it before a chance to suffer, I mean enjoy finding the solution.

                              Wrong is evil and must be defeated. - Jeff Ello

                              L Offline
                              L Offline
                              Lost User
                              wrote on last edited by
                              #20

                              Our AI teacher on CS faculty gave us this assignment (and other of similar type about 15 years ago) to promote analog type of thinking ... meaning that not everything is about zeros and ones in computer science.

                              1 Reply Last reply
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                              • M Member 11762424

                                if the light is incandescent or halogen, it will get hot if left on. so switch on the first switch, and get distracted for 10 minutes, switch it off, switch on the next one and race upstairs. If the light is on, it is that 2nd switch. If it is off but hot, it was the first switch. Else it is the third switch. If it's an energy-efficient bulb, this won't work.

                                J Offline
                                J Offline
                                Jorgen Andersson
                                wrote on last edited by
                                #21

                                And we have a winner.

                                Wrong is evil and must be defeated. - Jeff Ello

                                1 Reply Last reply
                                0
                                • P Peter_in_2780

                                  The classic solution (which I won't give away) may not work too well with modern LED globes! CFLs maybe. Cheers, Peter

                                  Software rusts. Simon Stephenson, ca 1994. So does this signature. me, 2012

                                  R Offline
                                  R Offline
                                  Rage
                                  wrote on last edited by
                                  #22

                                  Exactly what I thought, this "riddle" is going to die out...

                                  Do not escape reality : improve reality !

                                  1 Reply Last reply
                                  0
                                  • J Jorgen Andersson

                                    Downstairs in a house are three identical on-off switches. One of them controls the lamp in the attic. The puzzle is to work out which switch controls the lamp. The rules are as follows. You are allowed to manipulate the switches all you like, and then you are allowed a single trip to the attic. How do you do it? To clarify: When you are downstairs there is no way to see into the attic, or see reflected light from the attic. Once you have gone to the attic you are not allowed back to the switches. <edit>you can also assume original state of all switches to be off.</edit><hint>Otherwise it won't work</hint> Note: If you already know the answer, or reads the newspaper where I nicked the puzzle from, then please don’t write it up immediately in the comments! Give those who have never heard it before a chance to suffer, I mean enjoy finding the solution.

                                    Wrong is evil and must be defeated. - Jeff Ello

                                    R Offline
                                    R Offline
                                    R Erasmus
                                    wrote on last edited by
                                    #23

                                    Check the other rooms if their light go on/off?

                                    "Program testing can be used to show the presence of bugs, but never to show their absence." << please vote!! >>

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                                    • P Peter_in_2780

                                      The classic solution (which I won't give away) may not work too well with modern LED globes! CFLs maybe. Cheers, Peter

                                      Software rusts. Simon Stephenson, ca 1994. So does this signature. me, 2012

                                      G Offline
                                      G Offline
                                      greldak
                                      wrote on last edited by
                                      #24

                                      Should still work but may need to take quite a bit longer.

                                      1 Reply Last reply
                                      0
                                      • J Jorgen Andersson

                                        Downstairs in a house are three identical on-off switches. One of them controls the lamp in the attic. The puzzle is to work out which switch controls the lamp. The rules are as follows. You are allowed to manipulate the switches all you like, and then you are allowed a single trip to the attic. How do you do it? To clarify: When you are downstairs there is no way to see into the attic, or see reflected light from the attic. Once you have gone to the attic you are not allowed back to the switches. <edit>you can also assume original state of all switches to be off.</edit><hint>Otherwise it won't work</hint> Note: If you already know the answer, or reads the newspaper where I nicked the puzzle from, then please don’t write it up immediately in the comments! Give those who have never heard it before a chance to suffer, I mean enjoy finding the solution.

                                        Wrong is evil and must be defeated. - Jeff Ello

                                        B Offline
                                        B Offline
                                        b_in
                                        wrote on last edited by
                                        #25

                                        Firstly turn on switch1 for 1 minute, after 1 minute turn off the switch1, then turn on the switch2. go to the room and check the cases: case1: If bulb is on then switch2 is default switch. case2: Touch bulb by your hand if it is warm then switch1 is default switch. case3: If bulb is cold/normal then switch3 is default switch. default: No switch is working. ;)

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                                        • P Peter_in_2780

                                          The classic solution (which I won't give away) may not work too well with modern LED globes! CFLs maybe. Cheers, Peter

                                          Software rusts. Simon Stephenson, ca 1994. So does this signature. me, 2012

                                          D Offline
                                          D Offline
                                          Dan Neely
                                          wrote on last edited by
                                          #26

                                          CFLs still get hot enough to the touch that you don't want to replace them immediately after they fail. LED's are only marginally more efficient; half of the "bulb" ends up being a heat sink. Bean counters being what they are; I'd expect it to be the bare minimum size required and to still get nice and warm.

                                          Did you ever see history portrayed as an old man with a wise brow and pulseless heart, waging all things in the balance of reason? Is not rather the genius of history like an eternal, imploring maiden, full of fire, with a burning heart and flaming soul, humanly warm and humanly beautiful? --Zachris Topelius Training a telescope on one’s own belly button will only reveal lint. You like that? You go right on staring at it. I prefer looking at galaxies. -- Sarah Hoyt

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