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    • Hand Switch a light switch

      Which switch?

      1 November, 2004
      November 2004

       

      You've just moved into a new house, and know that one of the three switches on the panel by the front door turns on the light in the loft, but which switch? You don't want to keep climbing the four flights of stairs to the loft, so how can you work out which switch turns on that light while only making one visit to the loft?

      (You need to use something about the nature of light bulbs to help you.)



      If you are stumped by last issue's puzzle, here is the solution.

      For some challenging mathematical puzzles, see the NRICH puzzles from this month or last month.

      Solution link
      Which switch solution
      • Log in or register to post comments

      Anonymous

      16 June 2012

      Permalink
      Comment

      Let the three switches be A,B & C

      Turn on switch A...
      Wait for a while(until u think that the bulb gets hotter)

      Now turn OFF A and Turn ON B...
      Visit to the loft........

      If the bulb glows then it is Switch B
      else touch the bulb if it is hot then Switch A
      else Switch C

      • Log in or register to post comments
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