SOLUTION: A certain math class has 21 people and each must work a problem out on the board. Determine the number of different orders that are possible. I understand Permutations and Comb

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Question 496853: A certain math class has 21 people and each must work a problem out on the board. Determine the number of different orders that are possible.
I understand Permutations and Combinations but this is the only question that stumps me, if you could help me out. Thanks

Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
There are 21 choices for the 1st person
There are 20 choices for the 2nd person
There are 19 choices for the 3rd person
and so on, until
There is 1 choice for the 21st person
This is a string of AND's not OR's
( any 1 of 21) AND ( any 1 of 20) AND ( any 1 of 19 ) etc.
When choices are ANDed, you multiply the possibilities

This maxed out my little Staples 8 digit calculator. It
also equals +21%21+