Решение задачи N3840 теория вероятностей полная вероятн

3840. There are three batches of radio tubes, numbering respectively 70, 10 and 20 pieces. The probabilities that the lamp will last for a given time are equal, respectively, for these batches to 0.9; 0.8 and 0.5. 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)