Question

Signals
The king has 10 (different) colored flags that he uses to send coded messages to his general in the field. For example, red-blue-green might mean “attack at dawn” and blue-green-red may mean “retreat.” He sends the message by arranging three of the flags atop the castle wall.

The maximum number of such coded messages is _______.

(Give your answer as a whole number.)

Answer 1

10! /(10-3)! = 10!/7! = 10*9*8

Answer 2

Google "permutations" by the way.

Answer 3

I got 518400 but it's considered wrong.

Answer 4

90*8 - 720

Answer 5

10*9*8 = 720, not 518400

Answer 6

Hmmm. 518400 = (10*9*8)^2
Why did you use that?