Re: Interview Question-- Marble puzzle

Maybe I'm a little slow, but I still don't get it.

phil chang wrote:

> Darn, I didn't review my answer carefully enough before I sent it out before.
> Here's the correct answer.
>
> Divide the marbles into 3 groups of 4. Call them A, B, and C.
>
> Measure A against B.
>
> If they balance, the odd marble is in group C, and the solution from there is
> straightforward. Measure any 2 in C.

so measuring C1 vs. C2.

> If they balance, one of the remaining
> C's is the one. The 1 remaining weighing will tell us which one it is.

now I'm measuring C3 vs. C4. The weighing tells me C3 and C4 have unequal weights. How do I know that it's C3 that's heavier or C4 that's lighter? (Since we don't know if the odd marble is heavier or lighter)

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