SOLUTION: How many combinations of president and vice president can be made in a class of 21? Klreddick@AOL.com

Algebra ->  Permutations -> SOLUTION: How many combinations of president and vice president can be made in a class of 21? Klreddick@AOL.com      Log On


   

Question 552395: How many combinations of president and vice president can be made in a class of 21?
Klreddick@AOL.com
Answer by jim_thompson5910(35256) About Me  (Show Source):
You can put this solution on YOUR website!
P(n,r) = (n!)/((n-r)!)

P(21,2) = (21!)/((21-2)!)

P(21,2) = (21!)/(19!)

P(21,2) = (21*20*19!)/(19!)

P(21,2) = 21*20

P(21,2) = 420


So there are 420 different ways.