A professor gives his students 9 essay questions to prepare for an exam. Only 3 of the questions will actually appear on the exam. How many different exams are possible?

Answer: 84

Step-by-step explanation:

The total number of the questions is 9

Possible question is 3

This is combination

Therefore n=9 and r=3

Combination formula=n! / ((n-r) ! r!)

9C3=9! / ((9-3) ! 3!)

=362880 / (6! 3!)

=362880/4320

=84