Henry Ernest Dudeney/Puzzles and Curious Problems/288 - Seating the Party/Solution
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Puzzles and Curious Problems by Henry Ernest Dudeney: $288$
- Seating the Party
- On a family outing, Dora asked in how many ways they could all be seated.
- There were $6$ of them, three of each gender, and $6$ seats:
- one beside the driver, two with their backs to the driver, and two behind them, facing the driver,
- No two of the same gender were allowed to sit side by side.
- The only people who were able to drive were the men.
- So, how many ways could they all be seated?
Solution
The number of ways of seating the party is $144$.
Proof
There are three choices of drivers and three choices of women to sit beside him.
Anyone else can sit with their back directly to the driver; there are four choices remaining.
The one beside them must be of a different gender; there are two choices remaining.
The last two people have two ways to fill in the remaining seats.
Therefore the number of ways to seat the party is:
- $3 \times 3 \times 4 \times 2 \times 2 = 144$
$\blacksquare$
Sources
- 1932: Henry Ernest Dudeney: Puzzles and Curious Problems ... (previous) ... (next): Solutions: $288$. -- Seating the Party
- 1968: Henry Ernest Dudeney: 536 Puzzles & Curious Problems ... (previous) ... (next): Answers: $465$. Seating the Party