Question

For 3 person relay, a coach can choose from 4 of his top runners. How many different 3- person teams can he choose?

Answer 1

4 choose 3
= C(4,3)
= 4


e.g.
A B C D

you can choose any 3 out of those 4
which means one letter is left out for each choice,
since there are 4 letters,
the number of ways to leave one letter out is 4
tha is,
A B C
A B D
B C D
A C D

Answer 2

24