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Interview Question

Interview Plano, TX

The brain teaser: You have 9 rubber balls, and a scale. One

  of the rubber balls is weighted less than the others. You can use the scale twice. How do you find which ball is weighted differently?

Interview Answer

2 Answers


How showing that you can answer this question proves you can be a representative at FXCM or not is beyond me, but I actually got this answer correct in the interview: 1. Split the 9 balls into 3 groups. 2. Put two of the three groups on opposite sides of the scale. 3. If they are equal, the light ball is in the 3rd group, otherwise the light ball is in the higher group on the scale. 4. Now repeat the strategy by putting two balls of the light group on the scale. 5. Again, if they are equal, the light ball is the 3rd ball, not on the scale. If they are equal, the light ball is highest on the scale.

Interview Candidate on Sep 7, 2012

Why would they ask you a question like that? Jesus tap dancing christ. This is the worst company to work for.

Johnny on Feb 2, 2013

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