Решение задачи N5110 теория вероятностей

5110. In a batch consisting of 10 identically packaged articles, articles of two grades are mixed, and 6 of these articles are of the first grade, and the rest of the articles are of the second grade. Find the probability that two products taken at random will be of the 1st grade. Solved in two ways.

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