Engineering Board Exam Reviewer · Circular and Cyclic Permutations · medium

In how many ways can 7 different beads be strung on a necklace (the necklace can be turned over)?

  1. 720
  2. 360
  3. 5,040
  4. 180

Answer

B. 360

Solution

Circular arrangements: (7-1)!=720. Because the necklace can be flipped, each arrangement and its mirror image are the same, so divide by 2: 720/2=360.

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