Solution of problem N3900 probability theory total prob

Solution of problem N3900 probability theory total prob

3900. The box contains parts of three types: 40 parts of the first type, 50 parts of the second and 60 parts of the third, with 20, 40, 60% painted among them, respectively. Find the probability that the item extracted from the box is colored at random.

Additional information:

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