CA Foundation · Quantitative Aptitude · Permutations and Combinations
In how many different ways can 7 guests be seated around a circular dining table at a wedding reception in Lucknow, if only the relative positions of the guests matter?
The answer is 720. When 7 distinct people sit around a circular table and only relative positions matter, one person fixes the reference point and the other 6 can be arranged in 6! = 720 ways. Using 7! would count rotations as different.
- A5040
- B720Correct
- C840
- D360
Explanation
For n distinct people around a circle, the number of arrangements is (n-1)!. Here (7-1)! = 6! = 720. The value 5040 is 7!, which wrongly treats the seating as in a row.
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