February 2012

Switch on the lights


I have a lovely roof-top garden which is illuminated by three incandescent bulbs at three different corners.

However, the problem is that the switches of these bulbs are situated downstairs and I keep forgetting which switch corresponds to which bulb with the result that I switch on all the light bulbs thereby wasting a lot of power.

I have decided to mark the switches so that I light only that bulb which is situated in the corner where I wish to spend a pleasant evening.

But, I am a lazy person and do not wish to make two or more trips to the roof top to determine which switch corresponds to which bulb. I want to find this out by making only a single trip to the roof top (I am carrying out this experiment in broad daylight and, so, I cannot see which bulb lights up when I press on a switch while standing downstairs).

Anyway, can you help me determine which switch belongs to which bulb by making just one trip to the roof top?

Click here for the solution

Some useful links for
your career:

  • Union Public Service Commission - www.upsc.gov.in
  • IIT-Kharagpur - www.iitkgp.ac.in
  • Indian Statistical Institute - www.isical.ac.in
  • Indian Institute of Technology Madras - www.iitm.ac.in
  • Indian Institute of Management, Ahmedabad - www.iimahd.ernet.in
  • Indian Institute of Mass Commission - www.iimc.nic.in
  • IIT Bombay - www.iitb.ac.in
  • Indian School of Mines, Dhanbad - www.ismdhanbad.ac.in
  • Birla Institute of Technology, Ranchi - www.bitmesra.ac.in
  • Central Institute of Fisheries Nautical and Engineering Training - www.cifnet.nic.in
  • Indian Institute of Information Technology, Allahabad (Deemed University) - www.iiita.ac.in
  • Central Marine Fisheries Research Institute, Kochi - www.cmfri.com
  • Tata Institute of Social Sciences, Mumbai - www.tiss.edu

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