60 Fun Facts About Riddles and Brain Teasers

What was Oedipus's answer to the Sphinx's riddle about what goes on four feet, then two, then three?

Man: a baby crawls on all fours, an adult walks on two legs and the old lean on a stick. In the usual telling the beaten Sphinx then threw herself from her rock and died.

Which two sisters 'each give birth to the other' in a riddle from an ancient Greek tragedy about Oedipus?

Day and night: each gives birth to the other in endless turn, and both words are feminine in Greek, which makes them sisters. Some later accounts make it a second riddle of the Sphinx.

What did Samson's riddle 'Out of the eater, something to eat' describe?

Honey in a lion's carcass: Samson had killed a lion and later found bees and honey in its body (Judges 14); the Philistines got the answer only by pressing his wife.

What was the answer to the riddle that probably became the nursery rhyme 'Humpty Dumpty'?

An egg: the riddle probably played on 'humpty dumpty' being 18th-century slang for a short, clumsy person, who might survive a fall from a wall where an egg would not.

In the traditional answer to the riddle 'As I was going to St Ives', who is going to St Ives?

Just the narrator: the man, his wives and their sacks, cats and kits are only met on the road, so they are taken to be coming the other way and all the sevens are a decoy.

Which mathematician's book Liber Abaci has a sevens puzzle much like the rhyme 'As I was going to St Ives'?

Fibonacci: his Liber Abaci of 1202, the book that introduced Hindu-Arabic numerals to much of Europe, repeats the old sum of sevens. Counted in full, the St Ives rhyme comes to 2,802.

In Wonderland, what answer does the Hatter give to his own raven and writing-desk riddle?

He hasn't the slightest idea: when Alice gives up, the Hatter admits it, the March Hare adds 'Nor I', and she tells them off for wasting time on riddles that have no answers.

In Turandot, what is Calaf's answer to the riddle 'born each night, dying each dawn'?

Hope: 'la speranza' is the first of Calaf's three right answers. A suitor who gets one wrong loses his head, as the Prince of Persia does in Act 1.

What answers Turandot's second riddle: 'flickers red and warm like a flame, but is not fire'?

Blood: 'il sangue' is Calaf's second right answer. The third riddle, about ice that kindles fire, turns out to describe Turandot herself.

In an old German riddle, what is the 'featherless bird' that a mouthless woman eats off a leafless tree?

A snowflake: the leafless tree is a tree in winter and the mouthless woman is the sun, which 'eats' the snow by melting it.

In the widespread riddle 'White field, black seeds', what are the field and seeds?

A page and its letters: the white field is the page and the black seeds the letters; the Veronese Riddle (c. 800) adds oxen for the fingers and a plough for the pen.

What does a Rig Veda riddle mean by a 'twelve-spoked wheel, upon which stand 720 sons of one birth'?

The year: its twelve months are the spokes, and 360 days plus 360 nights make the 720 'sons of one birth' (Rig Veda 1.164.11).

What animal does the medieval riddle 'Four hang, two point the way, two ward off dogs, one dangles behind' describe?

A cow: the four that hang are her teats and the one that dangles behind is her tail. In a 13th-century Icelandic saga it is among some thirty-seven riddles that King Heidrek solves.

In the German riddle where Two-legs sits on Three-legs eating One-leg, what is the Four-legs that steals it?

A dog: Two-legs is a person on a three-legged stool, eating One-leg, a leg of meat. When the dog makes off with it, the stool becomes the weapon that wins it back.

In the Grimms' tale 'Rumpelstiltskin', what must the queen do within three days to keep her child?

Guess the imp's name: she has three days to name him, and succeeds only because her messenger overhears him singing 'Rumpelstiltskin' at his fire.

In the Monty Hall problem, which move wins two times in three?

Switching doors: your first pick is wrong two times in three, and each time the host, who must reveal a losing door, leaves the car behind the only door left. Sticking wins just one time in three.

Where did the 'missing' dollar go in the missing dollar riddle about three hotel guests and a bellhop?

Nowhere: the sum is a trick. The guests paid $27, which is the $25 in the till plus the bellhop's $2; adding his $2 to the $27 counts it twice, and the $30 is a red herring.

In the classic wolf, cabbage and third-passenger river puzzle, what does the farmer ferry across first?

The goat: it is the only passenger that can't be left alone with either of the others. The puzzle is over 1,100 years old, from a problem collection attributed to Alcuin of York.

At one move a second, about how long would a 64-disk Tower of Hanoi take?

600 billion years: the fastest solution takes 2 to the 64th minus 1 moves, which at one a second is some 585 billion years, roughly 42 times the age of the universe.

Which French mathematician sold the Tower of Hanoi as 'N. Claus de Siam'?

Édouard Lucas hid in plain sight: 'Claus' is an anagram of 'Lucas', and the full name rearranges to 'Lucas d'Amiens', after the city where he was born.

Which Greek hero's ship, its planks replaced one by one, gives its name to a famous puzzle about identity?

Theseus: Plutarch says the Athenians kept his ship for centuries, swapping each rotten timber for a sound one, until philosophers argued over whether it was still the same ship.

On an island where knights always tell the truth and knaves always lie, which statement can no islander make?

'I am a knave' can't be said: a knight would be lying and a knave would be telling the truth. Raymond Smullyan named the two tribes in his 1978 puzzle book What Is the Name of This Book?

Which mathematician proved that no walk could cross each of Königsberg's seven bridges exactly once?

Leonhard Euler: to prove it he ignored the map and kept only the land masses and the links between them, a move that founded graph theory.

The Zebra Puzzle is often called whose 'riddle', despite no evidence he wrote it?

Albert Einstein: legend says he wrote it as a boy, but the 1962 Life International version has a house where Kools are smoked, a cigarette brand launched in 1933, when he was 54.

In the 'bridge and torch' puzzle, which move beats the fastest walker escorting everyone?

Pairing the two slowest: with walkers who take 1, 2, 5 and 8 minutes, the quick pair shuttle the torch so the 5 and the 8 cross together, which takes 15 minutes against 17 for the escort plan.

Which phrase is often linked to the nine dots puzzle, a favourite of 1970s management trainers?

Thinking outside the box: the nine dots can be joined by four straight lines only if the lines run past the edge of the square the dots seem to form, which is the point the trainers were making.

The 2015 viral logic puzzle 'Cheryl's Birthday' came from a maths olympiad in which country?

Singapore: the puzzle was set for teenagers in the 2015 Singapore and Asian Schools Math Olympiad, but a TV presenter posted it online as a primary-school question and it went round the world.

Which paradox says an expected-value calculation suggests you should always swap, though the choices are symmetric?

The two envelopes problem: one envelope holds twice the other, so swapping seems to risk half to gain double. The same sum then tells you to swap straight back, and so on for ever.

Which term did Edward de Bono coin in 1967 for solving problems by unorthodox means?

Lateral thinking: de Bono applied it to everything. He once told British Foreign Office officials that Marmite might ease the Arab-Israeli conflict, by supplying zinc that he said a diet of unleavened bread lacks.

A riddle whose answer turns on a pun, like 'What's black and white and red all over?', is called what?

A conundrum, in the strict sense, is a riddle answered by a play on words: here 'red' is heard as 'read', and the answer is a newspaper.

A puzzle spelling words with pictures and letters, like a bee plus 'n' for 'been', is called what?

A rebus: the name is apparently Latin for 'by means of things', perhaps because pictures of things stand in for the words. One made of letters alone, like 'CU' for 'see you', is a gramogram.

In The Hobbit as it is now printed, what does Gollum promise Bilbo if Bilbo wins their riddle game?

The way out: Gollum agrees to guide Bilbo from the tunnels if he loses and to eat him if he wins. In the 1937 first edition he staked his ring instead, until Tolkien rewrote the scene to fit The Lord of the Rings.

In The Merchant of Venice, a suitor wins Portia by choosing the casket made of which metal?

Lead: its label warns that whoever picks it 'must give and hazard all he hath'. The gold casket holds a skull and a scroll that begins 'All that glisters is not gold'.

The Riddler's real name in the Batman comics is a pun on which word?

Enigma: the Riddler's name Edward Nigma (E. Nigma) puns on 'enigma'; he taunts Batman with 'Riddle me this'.

Who played the Riddler in the 1995 film Batman Forever?

Jim Carrey: his Riddler is a disgruntled Wayne Enterprises inventor who turns on Bruce Wayne after his boss rejects a gadget that beams television straight into the brain.

Which tenth-century manuscript, kept at an English cathedral, preserves nearly a hundred Old English riddles?

Exeter Book: one scribe copied out the whole anthology around 970, and it became the founding volume of the city's cathedral library, which still holds it.

Some of the earliest recorded riddles, on tablets nearly 4,000 years old, come from which civilisation?

Sumer: one riddle describes a house that one enters with eyes closed and leaves with eyes open. The solution written on the tablet is the scribal school.

'Riddle' is a cousin of which everyday verb, which once meant to advise or interpret?

Read: Old English rǣdels, 'counsel, conjecture, riddle', is kin to rǣdan, 'to advise, interpret, read'. It became 'riddle' when speakers took its final s for a plural and dropped it.

A puzzle like the St Ives rhyme, with houses, cats and mice, appears in which document over 3,500 years old?

The Rhind Papyrus: its Problem 79 lists 7 houses, 49 cats, 343 mice and so on up to 16,807 measures of grain. Its scribe, Ahmes, was copying a text older still, which has not survived.

What was Arthur Wynne's first modern crossword, published in the New York World in 1913, originally called?

A word-cross: Wynne's puzzle of 21 December 1913 was headed 'Word-Cross'. Within weeks the name had been flipped in print, by a typesetter's slip in one account and an illustrator in another, and 'Cross-Word' stuck.

Which puzzle first ran in an American magazine in 1979 as 'Number Place' before a Japanese publisher renamed it?

Sudoku: Japan's Nikoli found the puzzle in an American magazine in 1984 and retitled it with a phrase meaning the digits must stay single, later clipped to the name the world knows.

The Rubik's Cube was invented in 1974 by Ernő Rubik, who was a professor of what?

Architecture: Rubik built the first cube from wooden blocks held together with rubber bands, scrambled it, and then needed a full month to solve it.

The Sator Square, five Latin words legible in four directions, was found earliest at which site?

Pompeii: the oldest known examples were scratched there before Vesuvius buried the city, and they put ROTAS, not SATOR, on the top line.

Hat problems, where prisoners deduce their own hat colour from others' behaviour, belong to which class of brain teaser?

Induction puzzles: each prisoner reasons from what the others' silence shows they cannot know, so cracking the simplest case unlocks the next one up.

Which Indian classic has Yudhishthira win back his dead brothers by answering a lake spirit's questions?

The Mahabharata: one by one four Pandava brothers drink from the lake without answering and fall dead, and only Yudhishthira, who stops to answer first, gets them back.

Which biblical visitor tested Solomon's wisdom with hard questions in 1 Kings 10?

The Queen of Sheba: once Solomon had answered everything, she admitted that 'the half was not told me' and gave him 120 talents of gold and more spices than the kingdom ever saw again.

The liar paradox is often traced to Epimenides, who called the people of which island, his own, 'always liars'?

Crete: if Epimenides, a Cretan, was telling the truth, then he was lying too. The line was famous enough for the New Testament's letter to Titus to quote it.

Which Norse god, in disguise, poses riddles to King Heidrek in a 13th-century Icelandic saga?

Odin, calling himself Gestumblindi, watches the king solve every riddle, then wins with a question only he could answer: what he whispered in his dead son Baldr's ear.

In Zeno's famous paradox, which slow animal can swift Achilles seemingly never overtake?

The tortoise: given a head start, it has always crept a little further by the time Achilles reaches where it was. The modern reply is that those endlessly shrinking gaps add up to a finite distance.

A classic Chinese character riddle joins 'woman' and 'horse', pronounced mǎ, into which everyday word?

Mother: 'thousand li' hints at a horse that can run that far and 'thousand gold' is a fond name for a daughter. Woman plus horse writes mā, mother, with the horse there only for its sound.

In a classic bar puzzle, a customer asks for water, gets a gun pointed at him and says thanks; what was cured?

Hiccups were the customer's real trouble, and a sudden fright is as old a folk cure for them as a glass of water. Solvers usually reach the story by asking the host yes-or-no questions.

An Ewe riddle from West Africa describes a woman with 'water in her tank' who never visits the river; what is she?

A coconut carries its own supply, the liquid sealed inside its shell. Speakers of the neighbouring Logba language liked the riddle enough to borrow it.

A bat and ball cost $1.10 together, and the bat costs $1 more than the ball; what does the ball cost?

5 cents is right, because a $1.05 bat is then exactly a dollar dearer. Most people blurt out ten, which is why psychologists use the puzzle to test whether we check a gut answer.

A puzzle's tenant rides the elevator to the top only on rainy days; which object makes that possible?

His umbrella is the tool: the tenant is too short to press the top buttons by hand, so on dry days the ride stops partway up.

A lily-pad patch doubles daily and covers a whole lake on day 48; on which day was half of it covered?

Day 47 is right, since one more doubling turns half a lake into a whole one. The tempting day 24 treats the growth as steady when it is explosive.

In The Princess Bride's battle of wits, which of the two wine goblets had Westley secretly poisoned?

Both of them held iocane powder, so Vizzini's long chain of reasoning never mattered. His opponent claims to have built up an immunity to the poison beforehand.

In Monty Python and the Holy Grail, the bridgekeeper is undone by a question about the airspeed of which bird?

A swallow, and an unladen one at that. When King Arthur asks the keeper of the Bridge of Death to clarify, the keeper cannot answer and is thrown into the gorge himself.

In The Hobbit, Bilbo's last riddle to Gollum asks 'What have I got in my pocket?'; what was in it?

A magic ring was in the pocket, picked up by chance in the goblin tunnels. Gollum guessed the truth only when he went looking for his treasure and found it missing.

In the nursery riddle of Little Nanny Etticoat, 'the longer she stands, the shorter she grows'; what is she?

A candle fits every clue: her white petticoat is the wax and her red nose the flame, which burns her shorter by the hour.

A nursery riddle describes 'thirty white horses upon a red hill' that tramp, champ and stand still; what are the horses?

Your teeth are the horses and your gums the red hill, champing whenever you chew. One classic nursery collection spoils the fun by printing the solution as the rhyme's title.