Interview Question

Interview Las Vegas, NV

There are 7 balls - of which 6 are identical, one weighs

  slightly less. You have a two sided scale (like Lady Justice's) that you can use just twice. How do you find the odd ball?
Tags:
analytical, difficult
Answer

Interview Answer

2 Answers

0

I got this wrong. Right answer is you take one ball out randomly and weigh the rest. If they're equal, you're holding the odd ball. If not, take one ball out from the scale w lower weight and repeat.

Interview Candidate on Aug 20, 2011
1

You take away one ball then weigh 3balls and 3balls on the scale. If the on the scale the balls balance then the one ball that you took is the odd ball if not then you take group of the lighter weight of the 3 balls from and you take away one ball and weigh one ball to one ball out of that group and if those two balances out then the one ball you took away is the lighter odd ball if they don't balance then the one weighing less of the two you know is the lighter odd ball.

Nathan Pan on Oct 6, 2012

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