[shirleydmil]

How many different combination of 13 objects can you have?

[Capuchin]

Okay so visualise 1 object, you can have only one combination, obviously.
For two objects, you can have 2 combinations, either one way round or the other.
For three objects, you have 6 combinations, for each piece you start with, there are 2 combinations.
For four objects, there are 24 combinations, for each starting object, there are 6 combinations (as there are 3 other objects), so total = 4x6

you can continue this logic as far as you want, as long as all the objects are unique. The answer for n objects is 1x2x3x4... xn.

Hope this helps :)

[worthbeads]

13! (or 13 factorial) In other words, 13*12*11*10*9*8*7*6*5*4*3*2*1