Find the number of ways (combination) by which two prefects can be selected from a class of fifteen students?

Jerrycurl12

5 years ago

15C2=15!/13!2!

=15*14*13!/13!2!

=15*14/2
=15*7

=105

Emmyrosh

4 years ago

Total number of students = 15
no. to be chosen = 2
15C2
= 15!/(15-2)!.2!
= 15!/13!×2!
= 105 ways