Interview Question

Anonymous Interview Burlington, ON (Canada)

Three switches needs to be matched with three light bulbs

  in the other room that you cannot see into. You can only go into the room once. Initially the bulbs are turned off.
Answer

Interview Answer

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Turn on two switches, wait for 5 min and turn off one of the switch. Go to the room -
1.One bulb still lit, this corresponds to the switch which is still ON
2. Check the other two non-lit bulbs: the one which is still hot corresponds to the switch you just turned off.
3. The bulb which is non-lit and "cold" corresponds to the third switch you never touched.

Anonymous on Feb 13, 2014

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