The author discusses three different problems of drawing a black ball out of a bag with black and white balls. For each of the three problems he calculates the same probability, which shows a paradoxical situation. The probability of drawing a ball (1) does not depend on the way of drawing, that is, if we put the drawn balls back into the bag or not, (2) is the same for all draws, and (3) does not depend on adding or taking out balls (according to fixed rules).

Reviewer:

Peter Dürr (Linkenheim)