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Puzzles, Origami and Other Mind-Twisters


By EDWARD ROTHSTEIN
Published: April 3, 2006

ATLANTA — Two hundred green marbles are in a green jar, and 200 red marbles are in a red jar. Thirty marbles are removed from the green jar and put into the red jar, which is then shaken and stirred. Thirty marbles are then scooped from that mixture and put back into the green jar. Which jar has more of the wrong color marbles?
Simple, right? The scoop removes only a very small proportion of green marbles, so more green remain in the red jar.

Except that's wrong: both jars begin and end with 200 marbles, so any green marble missing from the green jar... see more