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HARD RIDDLES

175 Hard Riddles With Answers

Start with twenty calibration riddles, then move into longer adult riddles, story problems, lateral-thinking setups and the final impossible section.

Every answer stays hidden until you choose to reveal it. Numbering runs continuously from 1 to 175.

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Choose your difficulty

175 hard riddles across four increasingly difficult collections.

RIDDLES 1 TO 20

Hard Riddles to Start With

Twenty to calibrate against. If these come easily, skip ahead.

Try each one before opening the answer.

RIDDLE 1

I am the space that makes a door useless, and I am also the reason a door works at all.

RIDDLE 2

I am the smallest sound a person can make on purpose, and I travel further in a quiet room than a shout does in a loud one.

RIDDLE 3

I am written once, I am worth nothing on its own, and I turn a piece of paper into an obligation.

RIDDLE 4

I prove where you were by proving where you were not.

RIDDLE 5

I am useless to the person who wrote me and I only take effect once they can no longer explain what I meant.

RIDDLE 6

I hide a face by covering it and I reveal something about the person wearing me at the same time.

RIDDLE 7

I am a sentence that has to be read twice, and the second reading is the only one that counts.

RIDDLE 8

I am the smallest mark in a sentence and I have started lawsuits.

RIDDLE 9

I stop everything, and without me a sentence never ends.

RIDDLE 10

I hold your place by being left behind.

RIDDLE 11

I am a copy of a face made by someone who has never met it.

RIDDLE 12

I show the shape of a person and none of the person.

RIDDLE 13

I go up a house carrying nothing but what the fire has finished with.

RIDDLE 14

A farmer has seventeen sheep. All but nine of them run off. How many does he have left?

RIDDLE 15

I am the only part of the candle that has to be destroyed for it to work.

RIDDLE 16

I stand in the dark waiting, I am useless until someone points me, and I go out at the worst moment.

RIDDLE 17

I hang across a stage, I decide when a story starts, and I get the last applause of the night.

RIDDLE 18

I learn every line and I hope never to speak one.

RIDDLE 19

Mr and Mrs Doyle have six daughters, and each daughter has one brother. How many people are in the family?

RIDDLE 20

I keep time perfectly and I have never once told anybody what time it is.

RIDDLES 21 TO 75

Hard Riddles for Adults

Longer setups, and answers that depend on an assumption nobody stated.

Try each one before opening the answer.

RIDDLE 21

I sit in a groove, I am dragged in a spiral for twenty minutes, and I turn scratches into music.

RIDDLE 22

I am sent, I am never read, and everything depends on somebody noticing me at all.

RIDDLE 23

A woman shot her husband, held him under water for thirty seconds, then hung him up. Twenty minutes later they went out for dinner together.

RIDDLE 24

I get sent to prison for a crime, I serve the whole sentence, and I was never there.

RIDDLE 25

I am the only thing a thief can steal and leave behind at the same time.

RIDDLE 26

I am the reason a message survives being read by the wrong person.

RIDDLE 27

I have a face nobody has seen, I hold everything valuable in the building, and I only open for a number.

RIDDLE 28

I float on the surface doing nothing at all, and every ship in the channel depends on where I am anchored.

RIDDLE 29

A hiker walks one mile south, one mile east, and one mile north, and arrives back at the exact spot she started. She sees a bear. What colour is it?

RIDDLE 30

A father and his son crash their car. The father is killed instantly. The son is taken to hospital, and the surgeon on duty looks at him and says they cannot possibly operate, because that boy is their son. How?

RIDDLE 31

I am opened by everybody and I have never been closed by anyone.

RIDDLE 32

Two men enter a restaurant and both order the same soup. One takes a mouthful, leaves, goes home and takes his own life. Why?

RIDDLE 33

I have been standing here for a thousand years and I have moved several hundred miles.

RIDDLE 34

I turn a hundred separate people into one thing that reacts as a single body.

RIDDLE 35

I am the only witness who was present at every crime in the building and I cannot be questioned.

RIDDLE 36

I am the last thing built and the first thing seen.

RIDDLE 37

I am a promise that a stranger will accept a piece of paper as though it were valuable.

RIDDLE 38

I cost more to make than I am worth and everybody accepts me anyway.

RIDDLE 39

I am the thing you were looking for the entire time you were looking for something else.

RIDDLE 40

I take up no room in the suitcase, I am the only thing you are certain to bring home, and customs will not declare me.

RIDDLE 41

I run in every direction at once from a single point and I have never been anywhere twice.

RIDDLE 42

I am a wall that lets you see everything on the other side and stop nothing.

RIDDLE 43

I am the only building where everybody arriving is hoping not to stay.

RIDDLE 44

I have a hundred rooms, everyone in me is a stranger, and everyone leaves by Sunday.

RIDDLE 45

I take your money without a word, I never say thank you, and everybody is glad when I stop working.

RIDDLE 46

I am the shortest distance between two people and the longest to travel.

RIDDLE 47

I am proof of the crime and I am also the only thing that can clear you.

RIDDLE 48

A man is found dead in the middle of a field, holding an unopened package, with no other footprints and no injuries visible. What happened?

RIDDLE 49

A man walks into a bar and asks for a glass of water. The barman pulls out a gun and points it at him. The man says thank you and leaves. Why?

RIDDLE 50

A woman is found dead in a locked room with a puddle of water beside her and nothing else out of place. How did it happen?

RIDDLE 51

Two people are found dead on the floor surrounded by broken glass and water. Nobody else was in the house.

RIDDLE 52

A man dies in a room full of sawdust with a saw beside him and no wound.

RIDDLE 53

A woman hears her husband's voice on the phone say a single sentence, hangs up, and immediately calls the police to report a murder that has not happened yet.

RIDDLE 54

I am the only lie everybody agrees to believe together for two hours.

RIDDLE 55

I am rehearsed for six months and I am supposed to look like it just occurred to somebody.

RIDDLE 56

I arrive after the show is over and I am the entire reason the show happened.

RIDDLE 57

I am silent, I sit in front of a hundred musicians, and every sound they make is my responsibility.

RIDDLE 58

I am struck once and I give an entire orchestra its only agreed truth.

RIDDLE 59

I am the only instrument you cannot play badly, because being wrong is my entire function.

RIDDLE 60

I have twenty six ingredients and everything anybody has ever written.

RIDDLE 61

I hold three hundred years of a family, I fit on one page, and I only grow in one direction.

RIDDLE 62

I am the only thing a person owns before they are born and cannot use until they can read.

RIDDLE 63

I take a year to arrive, I last one day, and I bring the same number to everybody who was born on it.

RIDDLE 64

I am the only journey where the destination is the same as the departure and nobody complains.

RIDDLE 65

I am the loneliest object built by people, I left forty years ago, and I am still going.

RIDDLE 66

I am the boundary past which nothing you say can reach anybody, and I move away as fast as you approach.

RIDDLE 67

I am water in a desert that has never once been thirsty.

RIDDLE 68

I am the only road built to be abandoned.

RIDDLE 69

I mark the distance to somewhere you have not reached and stand still while you pass.

RIDDLE 70

I am a line agreed by people that the ground has never heard of.

RIDDLE 71

I am worth nothing after the moment printed on me and everything before it.

RIDDLE 72

I let one person through at a time and I only turn one way.

RIDDLE 73

I am the promise printed on a board, and I am wrong more often than any other document in the country.

RIDDLE 74

I am the only thing a station announces that nobody wants to hear announced.

RIDDLE 75

I hold your place in a line that has never moved and I will call your number eventually.

RIDDLES 76 TO 125

Long Hard Riddles

Story riddles, where the whole scenario has to be held in your head at once.

Try each one before opening the answer.

RIDDLE 76

Four prisoners are buried to the neck in a line, all facing the same way, with a wall between the fourth man and the other three. Two wear black hats and two wear white. Each can see only the hats in front of him, nobody can see his own, and they know the totals. The first to correctly call out his own hat colour frees them all. Speaking otherwise kills them all. Nobody speaks for a full minute, then one calls out correctly. Who, and how?

RIDDLE 77

A hundred prisoners are each given a number and led one at a time into a room holding a hundred closed boxes, each containing one number in a random order. Each prisoner may open fifty boxes looking for his own number, and must leave the room exactly as he found it. If every single prisoner finds his number they all go free. Random guessing gives them a vanishingly small chance. What strategy gives them better than thirty percent?

RIDDLE 78

A jeweller has ten bags of identical coins. Nine bags hold genuine coins weighing ten grams each, and one bag holds counterfeits weighing nine grams each. He has a digital scale that gives an exact reading, and he may use it once. How does he find the fake bag?

RIDDLE 79

A king has a thousand bottles of wine and one is poisoned. The poison kills within twenty four hours in any dose. He has ten prisoners and the feast is tomorrow. How does he find the bottle?

RIDDLE 80

Twenty five horses race on a track that fits five at a time, and there is no stopwatch. What is the fewest races needed to find the fastest three?

RIDDLE 81

A boat is floating in a swimming pool carrying a heavy stone. Someone lifts the stone out and drops it into the pool. Does the water level rise, fall or stay the same?

RIDDLE 82

Three friends pay ten pounds each for a room costing thirty. The manager realises the room is only twenty five, and sends five pounds back with a porter, who keeps two and returns one pound to each guest. Each guest has now paid nine, which is twenty seven, and the porter has two, making twenty nine. Where is the missing pound?

RIDDLE 83

A rope is tied tightly around the equator of a perfectly smooth sphere the size of the Earth. You add one extra metre of rope and lift it evenly all the way around. How high does it sit off the ground?

RIDDLE 84

Two candidates for a job are told to run a race in which the loser wins the position. Both stand still at the line for an hour. A passing stranger says four words and they both run flat out. What were they?

RIDDLE 85

A man has to cross a desert that takes six days to traverse, but he can only carry four days of supplies. He may cache supplies along the route and return for more, and he has as many identical helpers as he wants who face the same limits. How does he get across?

RIDDLE 86

An island holds a hundred people with blue eyes and a hundred with brown. Nobody knows their own eye colour, no mirrors exist, and discussing it is forbidden. Anyone who deduces their own colour must leave at midnight. A visitor says one sentence out loud: at least one of you has blue eyes. Everyone already knew this. What happens?

RIDDLE 87

Two ropes hang from a ceiling far apart, and you cannot reach one while holding the other. You have a knife and nothing else. How do you tie the two ends together?

RIDDLE 88

A man must transport a wolf, a goat and a cabbage, but this time the boat holds two items alongside him and the wolf now also eats the cabbage. He crosses in one trip. How?

RIDDLE 89

Three switches at the bottom of a tall building control three lights at the top, and the lift is out of order so you can only climb once. All three lights are new LEDs that give off no heat. How do you tell which is which?

RIDDLE 90

A woman buys a painting for seventy pounds, sells it for eighty, buys it back for ninety and sells it again for a hundred. What is her profit?

RIDDLE 91

A snail climbs a ten metre wall, rising three metres each day and sliding two metres back each night. How many days until it reaches the top?

RIDDLE 92

A clock strikes six in five seconds. How long does it take to strike twelve?

RIDDLE 93

You have an eight litre jug full of water and two empty jugs holding five and three litres. Divide the water into two equal parts using only the jugs.

RIDDLE 94

Two trains leave stations two hundred kilometres apart heading at each other, one at sixty and one at forty kilometres an hour. A bird flies from one train to the other at a hundred, turning instantly each time. How far does the bird fly before the trains meet?

RIDDLE 95

A hundred ants are placed randomly on a metre long stick, each facing either direction, walking at one metre a minute. When two meet they instantly reverse. How long until the stick is certainly clear?

RIDDLE 96

A cake has to be divided between two people who both suspect the other of greed. Neither trusts a third party. How do you make it fair?

RIDDLE 97

A camel is loaded with three thousand bananas and must walk a thousand kilometres to market, carrying at most a thousand bananas and eating one per kilometre travelled in either direction. How many bananas reach the market?

RIDDLE 98

Two guards, two doors, one truthful and one deceitful, and you may ask one question. This time both guards are allowed to refuse to answer if they wish. What do you ask?

RIDDLE 99

Twelve identical looking balls include one that differs in weight, but you are not told whether it is heavier or lighter. Find it in three weighings on a balance.

RIDDLE 100

A man is looking at a portrait and says that brothers and sisters he has none, but that man's father is his father's son. Who is he looking at?

RIDDLE 101

A prisoner is told he will be hanged on one weekday of the coming week, and that the day will be a complete surprise to him on the morning it happens. He reasons that it cannot be Friday, because by Thursday night only Friday would remain and he would know. Having ruled out Friday he rules out Thursday for the same reason, and so on back through the week, concluding he cannot be hanged at all. On Wednesday they hang him and he is completely surprised. Where was his reasoning wrong?

RIDDLE 102

A rich man builds a house where every wall faces south. A bear walks past the window. What colour is the bear, and why is this different from the earlier version?

RIDDLE 103

Three boxes contain two gold coins, two silver coins, and one of each. All three labels are wrong. You draw one coin from one box without looking inside. Which box do you choose?

RIDDLE 104

A woman has two children and you know at least one is a boy. What is the chance both are boys?

RIDDLE 105

A game show offers three doors, one with a prize. You pick one, the host opens a different door revealing nothing, and offers you the switch. Should you take it?

RIDDLE 106

A hundred people board a plane with a hundred assigned seats. The first passenger sits in a random seat. Every passenger after takes their own seat if free, and a random free seat if not. What is the chance the last passenger gets their assigned seat?

RIDDLE 107

A prisoner faces two guards, one who always lies and one who always tells the truth, but he may only ask one guard one question and the guards do not know which door he wants. He asks a single question and walks out safely. What did he ask that the earlier versions did not?

RIDDLE 108

A farmer wants to fence a square field and has enough wire for exactly one side to be a hundred metres. His neighbour offers to let him use an existing straight wall as one side, free. How much larger can the enclosed field be?

RIDDLE 109

A message says the treasure lies where the shadow of the tallest tree falls at noon on the shortest day of the year. The searchers dig there and find nothing. Why?

RIDDLE 110

A man walks into his kitchen, sees the window open, the safe empty and no sign of forced entry, and immediately knows the thief had a key. How?

RIDDLE 111

A body is found at the foot of a tall building with a suicide note. The detective examines the note, checks every floor, and arrests the caretaker. How did he know?

RIDDLE 112

A man calls a hotel from his room and says nothing at all, then hangs up, and this makes him safe. What was happening?

RIDDLE 113

A driver goes the wrong way down a one way street, straight past a police officer, and is not stopped. Why?

RIDDLE 114

A woman pushes her car until she reaches a hotel, then hands over all her money. Why?

RIDDLE 115

A man leaves his house, makes three left turns and returns to find two masked strangers waiting. Who are they?

RIDDLE 116

A woman is found dead in a field with an unopened parachute, and the investigation rules out both suicide and a faulty chute. What happened?

RIDDLE 117

Two men are stranded on an island with one boat that holds only one person. Both escape without either abandoning the other. How?

RIDDLE 118

A woman is told her husband died on a business trip. She has never met the caller, she has no evidence, and she immediately tells the police the caller is the killer. Why?

RIDDLE 119

A magician promises to tell any spectator the exact card they are thinking of, and does so every time without a plant or a marked deck. His only tool is the question he asks first. What was it?

RIDDLE 120

A lift is found stopped between floors with the doors open, a briefcase inside and no passenger. The building has no basement and the lift shaft is sealed. Where did the passenger go?

RIDDLE 121

A watchmaker is handed a clock that runs precisely two minutes fast every hour. It is set correctly at noon. When will it next show the correct time?

RIDDLE 122

A ship's rope ladder has rungs a foot apart and three rungs above the water. The tide comes in at a foot an hour for six hours. How many rungs are submerged?

RIDDLE 123

A man buys a horse for sixty, sells it for seventy, buys it back for eighty and sells it for ninety. Everyone at the table gives a different answer for his profit. What is it?

RIDDLE 124

A jar doubles its contents every minute and is full at sixty minutes. At what minute is it a quarter full?

RIDDLE 125

A room contains a hundred lockers, all closed. A hundred people walk through in turn. The first opens every locker, the second changes every second one, the third every third, and so on. Which lockers are open at the end?

RIDDLES 126 TO 175

Really Hard & Impossible Riddles

The final stretch: tougher setups, tighter wording, and riddles built to punish assumptions.

Try each one before opening the answer.

RIDDLE 126

I am the only word that becomes its own opposite when nothing at all is changed about it.

RIDDLE 127

I am spoken by everybody, written by nobody, and I change completely every hundred years without anyone agreeing to it.

RIDDLE 128

I am the only measurement that becomes wrong the more precisely you take it.

RIDDLE 129

I am the number of grains that makes a heap, and no one has ever been able to name me.

RIDDLE 130

I am true and I cannot be proved, and proving that about me is the whole reason anyone knows my name.

RIDDLE 131

I am a barber who shaves every man in town who does not shave himself. Who shaves me?

RIDDLE 132

I am the sentence that is false if it is true and true if it is false.

RIDDLE 133

I am a list of every list that does not contain itself. Do I contain myself?

RIDDLE 134

I always arrive exactly half way, and I have never once arrived.

RIDDLE 135

I hold more numbers than there are numbers, and I fit between nought and one.

RIDDLE 136

I am a hotel with infinite rooms, every one occupied, and I always have space for one more.

RIDDLE 137

I can be folded flat, I have one side and one edge, and cutting me down the middle gives one longer loop instead of two.

RIDDLE 138

I have no volume, no thickness and I still have a surface.

RIDDLE 139

I am a shape whose edge is infinitely long and whose area is finite.

RIDDLE 140

I am the amount you would pay to enter a game whose expected winnings are infinite, and almost nobody would pay more than twenty.

RIDDLE 141

I am the only thing that becomes less likely the more times it has already happened, according to everybody, and it never actually does.

RIDDLE 142

I am rare and I am dangerous, and testing accurately for me still means most positive results are wrong.

RIDDLE 143

I have two envelopes, one holding twice the other, and swapping always looks better whichever one you open.

RIDDLE 144

I am the only race where the faster runner never overtakes, provided you describe it in the right way.

RIDDLE 145

I am the same ship after every plank has been replaced, and I am also a different one.

RIDDLE 146

I am the choice that is worse for both of us and better for each of us alone.

RIDDLE 147

I am the pasture everyone is entitled to and nobody protects.

RIDDLE 148

I am the rule that a system cannot describe itself completely from inside itself, and I ended a century of hoping otherwise.

RIDDLE 149

I am the question you cannot answer by running the program, because running it is the question.

RIDDLE 150

I am a map that has to be four colours and never five, and it took a computer to prove me.

RIDDLE 151

I am the shortest route between many cities, and finding me for a hundred of them would outlast the universe by brute force.

RIDDLE 152

I am a note that was proved in the margin and the margin was too small.

RIDDLE 153

I am a conjecture about every even number, tested to enormous heights, and unproved for nearly three hundred years.

RIDDLE 154

I take any number, halve it if even, treble it and add one if odd, and I have always reached one, and nobody can say why.

RIDDLE 155

I am the word that sounds like what I describe and I have never once been onomatopoeic about myself.

RIDDLE 156

I am the only question to which the honest answer is always no.

RIDDLE 157

I am the only word you can add to any sentence to make it less true.

RIDDLE 158

I am the thing everybody in the room is thinking and nobody has said, and I get louder the longer that lasts.

RIDDLE 159

I am what makes a group of clever people reach a decision none of them agreed with.

RIDDLE 160

I am the reason the first number anybody says changes every number said afterwards.

RIDDLE 161

I am the evidence you went looking for, and I have never once let you down.

RIDDLE 162

I am obvious to everyone afterwards and invisible to everyone before.

RIDDLE 163

I make the least competent the most certain.

RIDDLE 164

I am the survivors' evidence, and every counterexample sank on the way here.

RIDDLE 165

I am the reason the planes that came back had holes in the wrong places.

RIDDLE 166

I am a prediction that comes true only because it was made.

RIDDLE 167

I am the measure that stops being useful the moment I become the target.

RIDDLE 168

I am the work that expands to fill whatever time you gave me.

RIDDLE 169

I am the part of the project that takes the second ninety percent of the time.

RIDDLE 170

I am the fence in a field with no purpose you can see, and the rule is not to remove me until you know why I am there.

RIDDLE 171

I am the cost you cannot recover and the one you keep counting anyway.

RIDDLE 172

I am the option you gave up, and I am the true price of the one you took.

RIDDLE 173

I am the thing so obvious that nobody wrote it down, and so nobody now knows how it was done.

RIDDLE 174

I am the only lock that opens for a person who admits they cannot open it.

RIDDLE 175

I contain my own solution, I hand it to you in the first line, and I have defeated you anyway. What am I?

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