Question

There are 22 students in Mario's class. Mario's teacher is planning to pair the students up for a project.

How many different combinations of pairs are possible?

Answer 1

\[\frac{ 22! }{ (22-2) !}\]

Answer 2

\[\frac{ n! }{ (n-r)!r! }\]

Answer 3

11
44
231
462

Answer 4

Thanks! Mind helping with some more?

Answer 5

This is combinations not permutations peru..

Answer 6

Okay so what is the answer then?

Answer 7

\[\frac{22!}{(22-2)! 2!} = \frac{22*21*\cancel{20*19*18...3*2*1}}{\cancel{(20*19*18*...3*2*1)}(2*1)} = \frac{22*21}{2} = 231\]