An examination consists of 11 questions.

Question

If exactly 9 questions must be answered, find the number of different orders in which a student can answer the questions

Answer 1

The number of ways of answering 9 out of 11 questions is the same as 2 out of 11=55, if it's just a question of the same combination of questions. If the order in which the questions are answered is important then we have to multiply by the number of permutations of 9 questions, and that comes to nearly 20 million (19,958,400).