Решение задачи N3565 теория вероятностей

3565. The pouch contains 10 identical cubes with numbers from 1 to 10. At random, three cubes are extracted one by one. Find the probability that the cubes with numbers 1, 2, 3 will appear sequentially if the cubes are extracted: a) without return; b) with the return (the extracted cube is returned to the bag).

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