Henry Ernest Dudeney/Modern Puzzles/169 - The Card Pentagon/Solution
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Modern Puzzles by Henry Ernest Dudeney: $169$
- The Card Pentagon
- Make a rough pentagon on a large sheet of paper.
- Then throw down the ten non-court cards of a suit at the places indicated in the diagram,
- so that the pips on every row of three cards on the sides of the pentagon shall add up alike.
- The example will be found faulty.
Solution
- Deal the cards $1$, $2$, $3$, $4$, $5$ in the manner indicated by the dotted lines
- (that is, drop one at every alternate angle in a clockwise direction round the pentagon),
- and then deal the $6$, $7$, $8$, $9$, $10$ in the opposite direction, as shown,
- taking care to start with the $6$ on the correct side of the $5$.
- The pips on every side add to $14$.
- If you deal the $6$, $7$, $8$, $9$, $10$ in the first manner and the $1$, $2$, $3$, $4$, $5$ in the second manner,
- you will get another solution, adding up to $19$.
- Now work with the two sets of numbers $1$, $3$, $5$, $7$, $9$ and $2$, $4$, $6$, $8$, $10$ in the same way
- and you will get two more solutions, adding, respectively, to $16$ and $17$.
- There are $6$ solutions in all.
- The last two are peculiar.
- Write in, in the same order, $1$, $4$, $7$, $10$, $13$ and $6$, $9$, $12$, $15$, $18$;
- also write in $8$, $11$, $14$, $17$, $20$ and $3$, $6$, $9$, $12$, $15$.
- Then deduct $10$ from every number greater than $10$.
Sources
- 1926: Henry Ernest Dudeney: Modern Puzzles ... (previous) ... (next): Solutions: $169$. -- The Card Pentagon
- 1968: Henry Ernest Dudeney: 536 Puzzles & Curious Problems ... (previous) ... (next): Answers: $398$. The Card Pentagon