CA Foundation · Quantitative Aptitude · Permutations and Combinations
Eight members of a family, including a married couple Mr. and Mrs. Iyer, sit around a circular table. In how many ways can they be seated so that Mr. and Mrs. Iyer sit next to each other?
The answer is 1440. Treating the couple as one block gives 7 units in a circle, arranged in 6! = 720 ways. The couple can sit in 2 orders within the block, so the total is 720 × 2 = 1440 seatings.
- A720
- B1440Correct
- C5040
- D10080
Explanation
Treat the couple as one unit, giving 7 units around a circle: (7-1)! = 720 ways. The couple can swap internally in 2! = 2 ways. Total = 720 × 2 = 1440. Option 720 forgets the internal arrangement of the couple.
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