NDA 2017 Maths · Mathematics · Permutations and Combinations · hard

The number of different necklaces that can be made with 7 distinct beads is

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Answer: (A) $360$

Arrangements in a circle:

(7-1)!=720

. A necklace can be turned over, so each arrangement equals its mirror image, and the count is halved:

\frac{720}2=360

. Option 720 treats it as a seating problem.

Original question written in the NDA 2017 Maths pattern and checked twice for the correct answer. Not an official question paper. How we write and check questions · Corrections policy · Report a mistake