There are $$24$$ four-digit numbers which is formed using each of the digits $$3$$, $$5$$, $$6$$ and $$9$$ once only. When all of these $$24$$ four-digit numbers are put in order from smallest to largest, which one is in the eighth position? 
Overseas Competition->Knowledge Point->Counting Modules->Questions Involving Enumeration->Enumeration
When put in order, the numbers are: $$3569$$, $$3596$$, $$3659$$, $$3695$$, $$3956$$, $$3965$$, $$5369$$, $$5396$$, $$5639$$, $$5693$$, $$\ldots $$ 