Решение задачи N3560 теория вероятностей

3560. In the urn there are 5 balls with numbers from 1 to 5. At random, 3 balls are extracted without returning. Find the probability of the following events: a) balls with numbers 1, 4, 5 will appear successively; b) the extracted balls will have numbers 1, 4, 5 regardless of the sequence in which they appeared.

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