Seven seated in age order
Seven people of distinct ages sit down at random in the seven seats of a round table. What is the probability that they end up seated in increasing order of age around the table (in either the clockwise or counter-clockwise direction)? The probability is for an integer ; find .
Show hints (2)+
- There are seatings. How many are increasing clockwise? (Fix the youngest's seat; the rest follow.)
- Add the counter-clockwise-increasing seatings (disjoint), giving favorable.
Answer
Reveal answer →Final answer
360
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