Goldman Sachs Interview Question
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Interview Question for Candidates Day Interviews for multiple areas (X-Div/Back Office) at Goldman Sachs:
You are in a room with 3 switches which correspond to 3 bulbs in another room and you don't know which switch corresponds to which bulb. You can only enter the room with the bulbs once. You can NOT use any external equipment (power supplies, resistors, etc.). How do you find out which bulb corresponds to which switch?
| Tags: | brain teaser, logic, case See more , See less 8 |
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4 of 4 people found this helpful
Turn on switch B.
Enter the room with the bulbs.
The hot bulb is A
The lit bulb is B
The dark bulb is C
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1 of 1 people found this helpful
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1 of 2 people found this helpful
1. Why do you think the light emits heat?
2. Why do you think you can touch the bulbs?
(3. If you're never going to enter the room again what's the point of knowing which switch goes with which light?)
The best you can do is reduce to guessing one of two bulbs.
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1. I guess you've never touched the outside of a light bulb after it's been on for awhile. The filament gets hot-it glows, the light we see is that glowing-the heat from from the glowing filament transfers to the glass-the glass is hot.
2. Why not? This is an exercise to demonstrate problem-solving ability, not a "MacGyver" episode. Who's to say the candidates didn't ask about the room's dimensions or where the bulbs were located, or that assumptions could be made in order to formulate an answer?
3. I think you missed the point of the question.
4. Sheesh.
3.
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15 of 15 people found this helpful
by Interview Candidate:
Turn one switch off after a few minutes.
Enter room with bulbs.
The bulb that is on is the only switch that is on.
The bulb that is off but hot, is the switch that has been turned off.
The bulb that is off and cold is the third switch.