Question 11540
Take any whole number; we'll call it n. Multiply all of the counting numbers from 1 through n. The product is called n factorial.

ex.

Find the number of ways you can arrange 5 people in a line. To find the number of possible arrangements for a number of items, you find the factorial of the number of items.

5!= 5 x 4 x 3 x 2 x 1 =120

So, 5 people can be arranged in 120 different lines.