Knotty Thinking

Dudeney dungeon

The “Death’s-head Dungeon,” from Henry Dudeney’s Canterbury Puzzles (1908), in which a youth rescues a noble demoiselle from a dungeon belong to his father’s greatest enemy:

“… Sir Hugh then produced a plan of the thirty-five cells in the dungeon and asked his companions to discover the particular cell that the demoiselle occupied. He said that if you started at one of the outside cells and passed through every doorway once, and once only, you were bound to end at the cell that was sought. Can you find the cell? Unless you start at the correct outside cell it is impossible to pass through all the doorways once, and once only.”

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Chess Detective Work

Retrograde analysis involves looking into a chess game’s past, rather than its future. Here’s an example from Henry Ernest Dudeney (1917):

Dudeney retrograde analysis

“Strolling into one of the rooms of a London club, I noticed a position left by two players who had gone. This position is shown in the diagram. It is evident that White has checkmated Black. But how did he do it? That is the puzzle.”

The solution is unique. Can you find it?

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“To — — –“

Here’s a valentine written by Edgar Allan Poe in 1846. His sweetheart’s name is hidden in it — can you find it?

For her these lines are penned, whose luminous eyes,
Brightly expressive as the starts of Leda,
Shall find her own sweet name that, nestling, lies
Upon the page, enwrapped from every reader.
Search narrowly these words, which hold a treasure
Divine — a talisman, an amulet
That must be worn at heart. Search well the measure —
The words — the letters themselves. Do not forget
The smallest point, or you may lose your labor.
And yet there is in this no gordian knot
Which one might not undo without a sabre
If one could merely comprehend the plot.
Upon the open page on which are peering
Such sweet eyes now, there lies, I say, perdus,
A musical name oft uttered in the hearing
Of poets, by poets — for the name is a poet’s too.
In common sequence set, the letters lying,
Compose a sound delighting all to hear —
Ah, this you’d have no trouble in descrying
Were you not something, of a dunce, my dear —
And now I leave these riddles to their Seer.

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Suburban Physics

You’re driving a car. The windows are closed. In the back seat is a kid holding a helium balloon.

You turn right. You and the kid sway to the left. What does the balloon do?

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Safety First

On an average weekend, the emergency room at the John Radcliffe Hospital in Oxford treats 67 children for injuries sustained in accidents.

On two recent weekends, however — June 21, 2003, and July 16, 2005 — only 36 children needed treatment. Can you guess why?

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Requiescat In Pace

William Andrews, Curious Epitaphs, 1899

A puzzle from 1796. “This curious inscription is humbly dedicated to the penetrating geniuses of Oxford, Cambridge, Eton, and the learned Society of Antiquaries.” Can you decipher it?

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Highway Robbery

A stranger called at a shoe store and bought a pair of boots costing six dollars, in payment for which he tendered a twenty-dollar bill. The shoemaker could not change the note and accordingly sent his boy across the street to a tailor’s shop and procured small bills for it, from which he gave the customer his change of fourteen dollars. The stranger then disappeared, when it was discovered that the twenty-dollar note was counterfeit, and of course the shoemaker had to make it good to the tailor. Now the question is, how much did the shoemaker lose?

— H.E. Licks, Recreations in Mathematics, 1917

Alcohol Problem

Fill one glass with wine and another with water. Transfer a teaspoonful of wine from the first glass into the second. Then transfer a teaspoonful of that mixture back into the first glass. Now, is there more wine in the water or water in the wine?

Most people will predict it’s the former, but in fact the two quantities will always be the same. Can you see why?