Решение задачи N3419 теория вероятностей

3419. The student came to the exam, knowing only 40 of the 50 questions in the program. The examiner asked the student 3 questions. Find the probability that the student has answered all the questions: a) using the classical definition of probability; b) conditional probability.

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