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# Changes

## Poison

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{{Hint| You could actually find the poisoned vial even if you have up to sixteen vials total. For seventeen vials, you would need an extra petri dish.}}

{{Solution | Allocate a number to each liquid (zero, one, two, three, etc).

Now let each dish represent a particular position in a four-digit binary number (so one dish represents the "eights" position, one dish represents the "fours" position, etc).

Place a particular liquid in a particular dish only if the number of that liquid, written in binary, has a "1" in the position represented by that dish.

Then read the results from the four dishes as a binary number, which will be the number of the liquid that is the poison.}}

==References==