Solution of problem N4587 probability theory

Solution of problem N4587 probability theory

4587. The urn contains 5 white, 20 red and 10 black balls, not differing in size. The balls are mixed thoroughly and then 1 ball is taken out at random. What is the likelihood that the ball drawn will be white or black?

Additional information:

Detailed solution. Decorated in Microsoft Word 2003 (Quest decided to use the formula editor)

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