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This is from my math book: 427) A box contains 1 black ball [#permalink]
28 Feb 2005, 11:55
This is from my math book:
427) A box contains 1 black ball and 9 white balls. Another box contains x black balls and the remaining balls are white, with a total of 10 balls. One ball is picked randomly from the first box and put into the second box, but its colour is not registered. Then one ball is picked from the second box. The probability that this last ball is black is: