A spoonful of cream is taken from a cup of cream and put into a cup of coffee. The coffee is then stirred. Then a spoonful of this mixture is put into the cup of cream.

Is there now more cream in the coffee cup or more coffee in the cup of cream?

There is exactly as much coffee in the cream as there is cream in the coffee.

You started out with a cup of liquid in each container, and ended up with a cup of liquid in aech container, so the amount of cream in the coffee must be equal to the amount of coffee "missing" (moved to the cream container).

This perhaps easier to see with a deck of cards. Separate the reds from the blacks. Then deal ten black cards to the red deck. Shuffle the red deck and deal ten cards to the black deck. Assume that "n" (we'll use 7 as an example) black cards remain n in the red deck. That means that 10 - n (3) black cards were returned to the black deck along with 10 - (10 - n) = n (7) red cards. So there are n black cards in the red deck and n red cards in the black deck.

Posted by TomM on 2002-06-22 06:12:36