Решение задачи N5193 теория вероятностей

5193. A batch of parts of 20 pieces containing 4 defective parts is subject to technical control. The quality of five parts randomly selected from this batch is checked. If there are at least two defective ones among them, then the batch is rejected. Find the probability that the lot will be rejected.

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