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Interview Question

Technical Support Engineer Interview Burlington, MA

If you had 9 marbles, all the same size. One is heavier

  than the rest. You have a balance scale. How do you determine the heavy marble in the least number of moves.
Tags:
logic, problem solving
Answer

Interview Answer

2 Answers

0

I suggested going in half.. 4 marbles each. The heavier group then divided 2 and 2, then 1 and 1. If it balanced, the extra is the heaviest. The answer was using 3 each. That would identify the set of marbles faster by one move.

Interview Candidate on May 29, 2012
4

The answer is 2.
Group them into 3 marbles each.
1. Weigh any 2 groups first
          - Find the heaviest group. If both are equal then the 3rd group is heaviest.
2. Now follow step 1 with 1 marble and you can find the heaviest.

Shakthi, Amazon on Jun 5, 2012

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