MathDB

Nine balls numbered

1,2,\cdots,9

are put on nine poines that divide the circle into nine equal parts. The sum of absolute values of the difference between the number of two adjacent balls is

S

. Find the probablity of

S

takes its minumum value. Note: If one way of putting balls can be the same as another one by rotating or specular-reflecting, then they are considered the same way.

Problem Statement