Question

Mr. Edge needs 5 students, who will be arranged from tallest to shortest, for a demonstration. He has 21 students in his class. How many different combinations of students are possible for the demonstration?

Answer 1

21C5


= 21!
-----
16! 5!

Answer 2

or you can write it as

21*20*19*18*17
--------------- = 21*19*17*3
5 *4*3*2*1

Answer 3

5*(21*20*19*18*17) = 12209400