Question 580623
<pre>
The answer would be 8! if the s's were all distinguishable, e.g., of 
different colors.

Since they are not distinguishable, 8! counts each arrangement 4! times too 
many, because in each arrangement there are 4! ways the 4 s's could be arranged
within that arrangement, if they were of different colors.  To eliminate
duplications in this case when they are not distinguishable, we must divide the
8! by 4!:

Answer:  {{{8!/4!}}} = {{{(8*7*6*5*4*3*2*1)/(4*3*2*1)}}} = {{{(8*7*6*5*cross(4)*cross(3)*cross(2)*1)/(cross(4)*cross(3)*cross(2)*1)}}} = 8·7·6·5 = 1680

Edwin</pre>