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Assume the cups each contains 90 units of liquid, and a spoon will fit 10 units (these numbers are used for convenience, the solution will work with any numbers)
After we put the spoon of cream into cofee, the coffee cup has 90 units of coffee and 10 units of cream. The cream cup has 80 units of cream.
If we stir the coffee cup thoroughly and take a spoonfull from it, the spoon full will contain a representative proportion of each liquid: 9 units of coffee and 1 unit of cream. (Thus 81 and 9 units of each is left in the cup.)
Pouring the liquid in the spoon back into the cream cup will yield 81 units of cream and 9 units of coffee in that cup.
Thus the proportions in both cups will be identical. |
