Stock Lateral Thinking Puzzle
The trickier variant of the Stock Puzzle
where the solution doesn't just require the application of logic and reasoning but the ability to think of things in another way. Frequently they are presented to appear like a difficult regular puzzle, but with a trick solution that is simple but not obvious.
Can sometimes be frustrating as it is often perfectly possible to construct a solution that explains all the presented facts in an unconnected way, but isn't the "right" answer that explains things by tying everything together.
As there are entire websites dedicated to building collections of lateral thinking puzzles, please limit examples to puzzles that have been featured in the media (somewhere other than puzzle books).
St. Ives Puzzle
As I was going to St. Ives, I met a man with seven wives. Each of the wives had seven sacks, each of the sacks had seven cats, each of the cats had seven kits. Kits, cats, sacks and wives, how many were going to St. Ives?
Solution: One: you are, everyone else is going the other way. For those interested, there is 1 man, 7 wives, 49 sacks, 343 Cats and 2401 kits, making a total of 2801 going away from St. Ives (2800, not counting the man). Some versions add "Each of the kits have 7 mitts" which would be an extra 16807 mitts for a total of 19608. Depending on the wording, this can be something of a cheat, as it's never specified what direction the others were going, if any.
- A variant asks instead, "How many T's are in all of that?", seemingly turning the numbers into a red herring. It is, but not in the way it appears. There are two T's in "all of that".
- Die Hard with a Vengeance: As part of Simon's game, Carver and McClane must solve the riddle and dial him back on 555-[The answer] before a bomb explodes. They get the answer right (555-0001) but are told they were too slow. However, there is no bomb because "I didn't say 'Simon Says'"
- Perplex City
- Knights of the Old Republic: Thankfully, the questions are for what is essentially a Jedi placement exam, so there are no "wrong" answers - but the lateral ones imply you're a character who prefers thinking your way out of problems, as opposed to finessing or forcing.
- Lest we not forget about the riddle that you can ask the prisoner in the mysterious box to get yourself free. note
- Sesame Street: The girl calculates the total number of people as the song is sung the second time and reveals her answer after being told the trick.
- And again with Kermit singing it as a song, with Grover frantically trying to keep track of the total.
- Of course, if you interpret the last sentence to mean, Out of the kits, cats, sacks and wives, how many were going to St Ives, the answer is zero.
How do you measure exactly 4 gallons using only a 3 and a 5 gallon jug?
Solution: Fill the 3, empty it into the 5 gallon, then refill the 3 gallon and fill the 5 gallon to the brim. You now have 1 gallon in the 3 gallon. Empty the 5 gallon jug, then put the remaining 1 gallon from the 3 gallon into the 5 gallon, refill the 3 gallon and empty into the 5 for exactly 4 gallons.
- Or fill the 5 gallon jug, empty it into the 3 gallon jug and throw the 3 away, you now have 2 gallons in the 5 gallon jug. Put those 2 gallons in the 3 gallon jug, then fill the 5 gallon jug again; now you have 2 gallons in the 3 gallon jug and 5 in the 5. Fill the 3 gallon jug with the water from the 5 gallon and throw the water from the 3 gallon jug away, you have exactly 4 gallons in the 5 gallon jug.
This has its own page as a Stock Puzzle
, as it's somewhere between a lateral thinking puzzle and a regular logic puzzle.
It's really about linear Diophantine equations, which are solvable by Euclid's algorithm using Bezout's lemma.
For examples of this puzzle, visit its page
How Many Drivers?
You're driving a bus to London with 8 passengers. At the first stop half of them get off and twice that number get on. At the next stop 1/3 of them get off and 3/4 the number of remaining passengers get on. At the last stop before London 5 people get on. How many people are driving the bus when it reaches London?
Solution: One, buses only have 1 driver regardless of the number of passengers. One variant is asking how many stops the bus made. Other variants include asking the age or sex of the driver. The answer is whatever your age or sex is as 'you' are driving the bus.
- The Touhou fan video "Cirno's Perfect Math Class" has a modified version of this puzzle (they wanted the number of people in total, rather than the number of people left on the bus); the answer Cirno gives is zero, because "there are no buses in Gensokyo". Given that Cirno is The Ditz, the absurdity of the answer makes sense in its own way.
The Doctor's Son
A man and his son are in a car accident and the man is killed. The boy is rushed to hospital. The doctor takes one look at him and says "I can't operate on this child, he's my son!" How is that possible?
Solution: The doctor is the boy's mother. The puzzle plays on people's tendency to assume certain gender roles unless explicitly told otherwise.
- Equally effective is the gender-flipped variation, where it is the boy's mother killed and a nurse objecting to the operation.
- Used in a "Woman's Lib" episode of All in the Family, when Gloria asks the riddle of the rest of the family. Edith gets it right.
- Used in an episode of The Cosby Show. In the setup, they refer to the doctor as "The old surgeon" and Cliff insists that the only reason he didn't get it is that no woman would allow herself to be referred to as "old."
- A variant with a female circus performer was used in an Encyclopedia Brown story.
- This riddle and several other listed here are lampshaded in The Office (US) Season 3 Episode 5 - "The Initiation". Dwight is attempting to teach Ryan - padawan style - the ways of the (sales) force, and is testing his intellect with a series of these hoary old riddles. Ryan knows them all and Dwight gets very frustrated until by the end, Dwight only has to say "A hunter..." and Ryan answers: It's a polar bear because you're at the North Pole.
- Hank is asked this one in an episode of Corner Gas, and ends up suggesting that the doctor is a ghost. Brent didn't get it either and asks for clarification of why Hank's theory couldn't be true.
- The children's toy robot 2-XL asked this riddle, asking the child whether the story was possible or not. After revealing the answer the robot broke down laughing at you.
- This one's lost a bit of the challenge, as it's perfectly reasonable to believe the boy might have two fathers. Or two mothers for that matter.
- There's a variation that goes as follows: A man, his wife, and their son are in a car accident. They are all rushed to the hospital and the doctor says, "I can't operate on him, he's my son." Solution: The doctor is the man's father and the boy's grandfather.
Various trick puzzles where it looks like there is a simple answer but it is in fact an invalid question:
- Who's buried in Grant's Tomb? Answer: No one is buried, but Grant and his wife are entombed there.
- This riddle was popularized by Groucho Marx on his game show You Bet Your Life, is "Who is buried in Grant's Tomb?" Though the proper answer is "nobody" Groucho would usually accept just "Grant." Groucho would ask this question to contestants to ensure that they won something on his show. It can also be a snide trick question: When the responder answers "Ulysses Grant," he can be termed wrong for forgetting or not knowing that Julia Grant is there also.
- Then shouldn't it be "Grants' Tomb"?
- This was averted in an episode of The Golden Girls, when it was the answer to Final Jeopardy in Dorothy Zbornak's dream sequence. Rose Nylund's response, "Who is Cary Grant ?" is deemed to be the correct response by both host Alex Trebek and series creator Merv Griffin.
- "George Washington!"
- Sometimes, people are tripped up because the answer of "Grant" seems too obvious. They assume that there must be a historical fact here they don't know, like maybe there was a mixup and the wrong body was placed in Grant's tomb. So they wind up guessing on something ridiculous and look silly.
- If a plane crashes exactly on a border, where are the survivors buried? Answer: The survivors are still alive and don't get buried anywhere.
- Implied in the cold open of an episode of Batman: The Brave and the Bold. The Riddler has Batman and Booster Gold chained up on a mock game show set, and gives Batman an electric shock for each question Booster gets wrong. A montage of the Riddler telling Booster the answers to questions he missed includes "You don't bury survivors."
- This one comes up in Corner Gas, the same episode as the Doctor one above, and again Hank screws it up. He first asks whether the plane is distributed more on one side than the other, and then when Karen emphasises the word "survivors", he answers. "Oh! One on each side."
- Also comes up in the deleted final scene of Die Hard with a Vengeance. Simon gets it right instantly.
- If a rooster lays an egg on the exact peak of a barn, which side does it fall? Answer: Roosters don't lay eggs.
- On an episode of The Simpsons Bart is dropped a grade and Lisa bumped up, leaving them both in the same class. This question stumps Lisa, but Bart gets it because he heard it the last time he was in that grade.
- Again used in the Corner Gas episode, and Hank's answers include "The Alberta side," (referring to the plane crash example above). "The roof is flat," and "The egg is square!"
- A variation of this was done in an ad in Australia in the late '90s/early '00s, for Smarties, if memory serves. "If a Daddy bull drinks 8 litres a day and a baby bull drinks 4 litres a day, how much does a Mummy bull drink?" The correct answer is that a 'Mummy bull' is an oxymoron - bulls are male cattle.
- Another similar one is "What is the colour of an egg laid by a peacock?"
- Additionally, the phrasing of this and other riddles means it would be perfectly valid to point out that saying the rooster doesn't lay eggs doesn't render the question invalid - if makes "a rooster lays an egg..." a premise and the rest of the question hypothetical, as in, "Roosters don't lay eggs, but if a rooster did, it could roll either way, and that's the question that was asked." See Many Questions Fallacy.
- How many animals of each kind did Moses bring on the Ark with him? Answer: Moses didn't have an Ark - at least, not one of the sort that animals could be put aboard, which was actually Noah's claim to fame.
- Is the capital of Kentucky pronounced 'LOU-ee-vil' or 'LEW-iss-vil'? Answer: Neither, since the capital of Kentucky is Frankfort. (And it's pronounced 'FRANK-furt', though people not from around there might not know that.)
- Assuming that Louisville actually was was the capital of Kentucky, the answer would still be neither, since even the least nitpicky Kentuckian would tell you that Louisville is properly pronounced LOU-uh-vuhl.
- Also commonly done with Florida and Miami, or with New Orleans, LA.
- How much dirt is there in a hole 2 meters by 2 meters by 2 meters? Answer: There isn't any dirt in a hole.
- Is it legal for a man to marry his widow's sister? Answer: No, because he's dead.
- Is it correct to say "the yolk of eggs is white" or "the yolk of eggs are white"? Answer: Neither, the yolk of eggs is yellow.
- Mentioned in one Miss Marple story, where she compares it to the mystery, which is also based on a trick question.
- In answer to the Red Herring question, when making a statement about the color of the yolk of eggs, under most prescriptive systems of English grammar one says "the yolk of eggs is." The subject is yolk, which is singular. Of course, many perfectly valid dialects do not necessarily preserve this distinction, and many others allow or require the verb to agree with "eggs" instead of "yolk".
- Actually, the correct way in proper English - written grammar is constant, after all - is "are". There is the implicit that you are saying all yolks of all eggs are one colour. Therefore, you are referring to multiple yolks, despite only saying "yolk" (though it would be better phrased to say yolks as well), and so must use the plural. It is 'less correct', but still correct, to say "yolk of eggs" because noun-noun agreements aren't necessary in English, unlike other languages. The best way to explain this is using the exemplification that in English the term 'United States' is used. The Spanish term? 'Estados Unidos'. Unido means United and Estado, State - in Spanish, because there are multiple States they have to be the Uniteds States, which sounds like nonsense.
- If it takes six men six hours to dig six holes, how long does it take to dig half a hole? Answer: You can't dig half a hole. (Trivia game Mindtrap adds "A hole is a hole.")
- If you have a cube, each edge two inches long, how many total square inches are there among all eight sides? Answer: Hard to say, since cubes have six sides.
- Cubes have six faces; the number of sides is twelve, though the more proper term would be edge
- A family of four wants toast for breakfast. The two children want one piece of toast each and the parents want two pieces of toast each. How many pieces of toast did they put into the toaster?/If roast goes into a roaster, what goes into a toaster? Answer: Toast does not go into a toaster. Bread does.
Tricks With Words
Often the trick is that the question being asked isn't actually the one you think due to tricky phrasing. Many of these are heavily dependent on the use-mention distinction
, and hence work best when spoken aloud, as proper grammar necessitates the use of inverted commas which would give the game away.
- Floccinaucinihilipilification is a long word, how do you spell it? Answer: I, T spells "it".
- In a similar vein: "Railroad crossing, look at the cars; can you spell that without any R's?" Obviously, the answer is "T-H-A-T".
- Think of words that end with the letters "gry". "Angry" is one, "hungry" is another. What is the third word in the English language?" The answer is "language" - there are, of course, no other actual English words with the suffix "-gry". note note 2
- Curiously, this puzzle was invented by mistake. The original version merely asks for the third word containing "gry", which is "gryphon". Someone asked for a third word ending in "gry" by mistake, and since there isn't one, several trick answers (of which the "language" one is the most common) were invented to fill the vacuum.
- There is also "anhungry", which was used by William Shakespeare in Coriolanus (Act I, scene i, line 209). It means "hungry".
- Planescape: Torment had this very puzzle. Being based on Dungeons & Dragons rules, you had to solve it via your character's stats and not "your" own knowledge.
- xkcd gives the appropriate response to this kind of trickery.
- In the days of Usenet, the regulars of rec.puzzles coined the word "nugry" to mean a newbie who posted a puzzle which was already in the FAQ — especially the "gry" puzzle — to rec.puzzles.
- Raymond Smullyan's What is the Name of This Book? includes puzzles which take the reader to an island of Knights and Knaves. One puzzle reads: "This time you come across just one inhabitant lazily lying in the sun. You remember that his first name is either Edwin or Edward, but you cannot remember which. So you ask him his first name and he answers 'Edward.' What is his first name?" Answer: It's Edwin, because he was lying.
- If two's company, and three's a crowd, what are four and five? Answer: Nine.
- What is the difference between here and there? Answer: The letter "t".
- What is the beginning of eternity, and the end of time and space? Answer: The letter "e".
- Alternatively, you can add on "The beginning of every end, and the end of every race."
- * In Harry Potter and the Goblet of Fire, the second part of the sphinx's riddle is "tell me what is the last thing to mend, the middle of middle and end of end". Since the answer of the entire riddle is spider, the answer to the riddle is the letter "d", which is the last letter of the word mend, the middle letter of the word middle, and the last letter in the word end.
- What can be found in the middle of water? Typical answers would include "an island" or "Fish" ... The right answer is the letter "t".
- I have sixty cups. Two drop to the ground and shatter. How many do I have left? Verbal only, as the answer is 4. It's six teacups.
- You have a kerosene lamp, a wood stove, and a fireplace, and you have only one match to light them all with. What do you light first? Answer: The match, because its what you're going to use to light the others. The way the question is phrased it can sound like 'Which one of the three items is the first one you light with the match?', but its actually asking 'Out of everything present, which object is lit first?'
How is this situation possible?'
- Two coins add up to 30 cents and one of them isn't a nickel. What are they? Solution: A quarter and a nickel. One of them isn't a nickel, the other one is.
- Or, you use a 20 cent and a 10 cent coin. Euro-cent.
- British variant: 60 pence, of which one coin isn't a 10p. 50 + 10 Or 25, of which one isn't a 5. 20 + 5
- Scrubs: Used by JD to trick the Janitor and Troy with this puzzle, who are thoroughly confused by the wordplay. Their solution involves scouring a book for coin collectors, finding and pointing out a coin that the book prices at 29 cents, and are enraged when JD explains the real answer. Their response at the end of the episode is to pose their own puzzle. "Two guys destroyed your bike with a softball bat and a crowbar, one of them wasn't me." This happens TWICE.
- An episode of The Cosby Show has a member of the family tell this riddle as part of a bet.
- An episode of The Office (US) has Dwight tell this riddle to Ryan, but he isn't fooled and answers correctly. Dwight is rather annoyed by that.
- Two girls look exactly alike, they were born on the same day, to the same mother, within an hour of each other, but they are not twins. How is this possible? Answer: They are two out of a set of triplets.
- Or quadruplets, or quintuplets, or...
- Jennifer is 20 years old in 1980, but 15 years old in 1985. How? Answer: Because she's living in the years Before the Common Era/Before Christ. (Though if that's the case, it's unlikely she would be named Jennifer.)
- Alternatively, 1980 and 1985 are apartment numbers or street codes. She simply moved some time after she turned 15.
- A cowboy rides into town on Friday. He stays three days, then rides out of town on Friday. How? Answer: The horse's name was Friday.
Which of these two weighs more?
- The most common form of the question is "A pound of gold or a pound of feathers"? The question is designed to play on the listener's inherent association of gold being heavier than feather. Standard Solution: They both weigh the same since they're both a pound. However, not all examples are that easy to decipher. One standard solution subversion: The feathers are heavier, since precious metals like gold are measured in Troy weight, not avoirdupois pounds (one Troy pound being about 370 grams, and one avoirdupois pound being around 450 grams).
- Alternatively, the phrasing could imply a quantity worth a british pound. How many feathers can you buy for a pound?
- A standard way of playing it for laughs is answering "Drop them on your toes, and you'll find out."
- Another variation is "which is lighter, a pound of white feathers or a pound of black feathers"? The white feathers are lighter in color.
- Inside Man has the bank robber ask the question of which weighs more: "all the trains that pass through Grand Central Station in a year - or the trees cut down to print all U.S. currency in circulation?" They think it's the former once they figure out the U.S. currency part, but one of the cops is smart enough to recall the robber said it was a trick question and the answer is always they both weigh the same, before deducing both answers neither quantity exists: U.S. currency is made of cotton and Grand Central Station is the informal name of Grand Central Terminal.
- When Jerry rhetorically asks Danny this question in Nukees, Danny points out, after some caveatsnote , that a pound of lead would displace less air, and therefore weigh more.
What kind of bear were they hunting?