Решение задачи N3839 теория вероятностей полная вероятн

3839. There are three batches of radio tubes, numbering respectively 20, 70 and 10 pieces. The probabilities that the lamp will last for a given time are equal, respectively, for these batches to 0.9; 0.6 and 0.8. Find the probability that a selected lamp of 100 will work at random for a given time.

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