Three black and three white beads are arranged on a string forming a circular bracelet. How many different color combinations are possible?

arrange the beads on the string from left to right ..

number of ways = 6!/(3!3!) = 20

but when we connect the string to make the bracelet, it does not matter if we go left to right or right to left,
So the number of bracelets possible is
20/2 = 10