Two tumblers, I and II, contain equal volumes of pure liquids A and B respectively.
A spoonful of liquid A is taken from tumbler I and transferred to tumbler II.
The contents of tumbler II are stirred.
A precisely-equal spoonful of the contents of tumbler II is now transferred to tumbler I.
At the end of this operation, which of the liquids is the less contaminated?
(Iíll explain a few days from now why I selected this question.)