Oil and Vinegar Problem

Two similar vessels contain exactly similar volumes of two different liquids. We shall call them oil and vinegar for convenience, but please ignore such considerations as density, viscosity and miscibility. A spoonful of oil is transferred to the vinegar, which is then stirred thoroughly to produce a consistent mixture. The same spoon is used to transfer a spoonful of the mixture to the oil, which is then stirred thoroughly.

Is the oil more contaminated than the vinegar, or the vinegar more contaminated than the oil, or what?

Now go to the answer.

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