# Math Help - Order of items around a circle

1. ## Order of items around a circle

I am trying to figure out how many ways 20 beads can be placed around a necklace, but i'm not really sure where to start.

Could someone give me a hint on this?

my thought is that it is 20! / 20

2. If we arrange twenty persons around a circular table, that can be done in
$19!$ ways.

But with beads on a necklace we can view it from two sides.
That is to say if we had three beads: red, green, & blue.
There would be only one necklace.

$\begin{array}{*{20}c}
{} & {red} & {} \\
{blue} & {} & {green} \\ \end{array}$
is the same as $\begin{array}{*{20}c}
{} & {red} & {} \\
{green} & {} & {blue} \\ \end{array}$