Circular permutations
Permutations and combinations · Mathematics
Study notes
Q: In how many ways can 6 people sit around a round table? What about 5 beads on a necklace? (a) Round table: (6-1)! = 120. (Fix one person; arrange 5 around: 5!.) (b) Necklace flips over: (5-1)!/2 = 12.