Circular permutations?

Question

i am actually preparing for the SAT math level 2 ....so tell me all that i need about it...i know that there isnt a whole lot of things that you need to know about it.....i was confused with the (n-1)! and (n-1)!/2,.....when do you use these two formulas..?

Answer 1

when there is difference between left and right then (n-1)! is applicable. e.g. sitting arrangement of people . Otherwise (n-1)!/2 is applicable