Logic Riddles with Answers
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Logic riddles reward patience. Every clue you need is right there in the question, so read it twice before you commit. Each one is labeled by difficulty, and the reveal walks through the deduction that cracks it. Filter to your level, grab the printable set, then tap to see how you did.
Logic riddles fall the moment you write down the assumption
Nearly every scene here is true as printed, and the wrong answer arrives when you add a line the text never wrote. The umbrella riddle never mentions rain. The pet shop owner promises a parrot that repeats every word it hears, and says nothing about whether it hears. A few cards run the other way: a rooster lays an egg, a banana waits atop a coconut palm. There the printed line is the impossible part, and naming it is the answer. Either way, write the premise your answer needs as a plain sentence and check it against the question.
The habit is one line of paper per riddle: write the fact your answer depends on, then reread the question hunting for it. If it is missing, you have found the door. The Hard tier changes the job: the premise is handed to you, the hats, the hourglasses, the seventeen camels, and the work is testing it. Trying one case and letting it fail is the move: nobody can truthfully call himself a knave, so a speaker whose sentence would make him one is lying.
What separates these from the tricky riddles is the job, not the length. A tricky riddle wants one assumption dropped and it is finished; here you state the premise and test what follows, sometimes across a whole rule set. The lateral thinking puzzles work scenes like these as a group game, where the answer arrives through yes or no questions rather than one written line.
- Riddle 17: most people say The umbrella was huge. Arguing about the size accepts a downpour the riddle never described, and the card already calls the umbrella small. Nobody got wet is the whole statement; the rain is your addition, and without it the umbrella has nothing to do.
- Riddle 28: most people say The buyer never spoke to it. A silent owner would explain a silent bird, but nothing in the scene keeps the buyer quiet. The promise covers every word the parrot hears, and hearing is the premise you supplied: a deaf bird keeps that promise perfectly while making no sound at all.
- Riddle 35: most people say Six rungs. Multiplying half a meter by six hours assumes the ladder hangs from something fixed to the seabed. Boat is the word that removes the sum, because a floating hull rises with the tide and carries the ladder up with it.
- Riddle 40: most people say The monkey. Ranking the three climbers by speed takes the promised banana at face value. Coconut palm is the pair of words to weigh: the tree named in the question grows one fruit, and it is not the one on offer, so the race has no prize to award.
Write down the premise your answer needs, then check whether the riddle ever stated it.
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1. A man is found dead in the middle of an empty field. Next to him lies an unopened package. How did he die? Easy
Most people first say: Struck by lightning
Need a hint?
Look up, not around.
Show answer
He fell from a plane. The package was his parachute, and it never opened.
Unopened is the detail everything hangs on. Ask why a package in an empty field matters at all, and the only object that kills by staying shut is a pack meant to open in the air.
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2. Romeo and Juliet lie dead on the floor. Around them are broken glass and a puddle of water. There is not a mark on their bodies. What happened? Easy
Most people first say: A poisoned couple
Need a hint?
Nobody said they were people.
Show answer
They were goldfish. The cat knocked their bowl off the table and they suffocated.
Not a mark on their bodies, a puddle, glass: the scene supplies the water and you supply the humans. Names from a play make you picture lovers, while the details describe a pet bowl tipped onto the floor.
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3. A boy and his father are in a car crash. The father dies. At the hospital the surgeon says, I cannot operate on this boy, he is my son. How? Easy
Most people first say: The boy's stepfather
Need a hint?
Question your first mental picture of a surgeon.
Show answer
The surgeon is his mother. The riddle only works if you assume surgeons are men.
Nothing in the scene is false, so the obstacle comes from a picture you supplied: a man in scrubs. Swap a woman into that role and every line of the story holds at once.
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4. A cowboy rides into town on Friday, stays three days, and leaves on Friday. How is that possible? Easy
Most people first say: He stayed a week
Need a hint?
Friday is not a day here.
Show answer
His horse is named Friday. He rode in and out on the same animal, not the same weekday.
Every reader files Friday under weekdays because the sentence is about a trip and its dates. The riddle never says day: it names the thing he rode, and a horse can carry a name that sounds like one.
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5. A truck driver goes the wrong way down a one way street, passes ten police officers, and none of them stop him. Why? Easy
Most people first say: The officers were off duty
Need a hint?
What exactly is he doing on that street?
Show answer
He is walking. The rule applies to driving, and he left his truck behind.
Truck driver is a job title, not a report of what he is doing right now. Once you stop putting him behind a wheel, the ten officers have nothing to write up, since the sign only governs traffic.
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6. A plane crashes exactly on the border between the United States and Canada. Where do they bury the survivors? Easy
Most people first say: On the Canadian side
Need a hint?
Read the last word again.
Show answer
Nowhere. You do not bury survivors, they are alive.
Where sends you to a map, so the argument becomes which country. Slow down on the last word instead: survivors are the people who lived, and nobody digs a grave for the living.
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7. An electric train is heading south at 100 km per hour. The wind blows from the north. Which way does the smoke drift? Easy
Most people first say: Toward the south
Need a hint?
What powers the train?
Show answer
There is no smoke. Electric trains do not burn anything.
Speed and wind direction are there to start a physics calculation. Electric is the word to reread: a motor running on current produces no exhaust, so the question asks you to track something that was never there.
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8. What can be broken without ever being held or touched? Easy
Most people first say: A heart
Show answer
A promise. Breaking it needs no hands at all.
Broken here is the figurative sense, the way a rule or a vow gets broken. Once you stop picturing a dropped plate, you are looking for a thing made of words, kept or ended by a decision rather than by hands.
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9. A man went out for a walk in heavy rain with no umbrella, no hat and no hood, yet not a hair on his head got wet. How? Easy
Most people first say: He stood in a doorway
Need a hint?
The rain did hit his head.
Show answer
He is bald. There was no hair to get wet.
Not a hair on his head is the line to read literally, because it never claims his head stayed dry. Rain soaked his scalp; the riddle is only counting hairs, and he has none to count.
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10. Feed me and I grow. Give me a drink and I die. What am I? Easy
Most people first say: A plant
Show answer
Fire. Fuel makes it bigger, water puts it out.
Feed and drink paint a creature with a mouth, so the contradiction to solve is a drink that kills. Something that eats yet cannot survive water is not alive at all; think of what wood feeds and a bucket puts out.
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11. If you have me, you want to share me. If you share me, you no longer have me. What am I? Easy
Show answer
A secret. Telling it is exactly what destroys it.
Want and lose in the same breath rules out any object, because giving a toy away leaves the toy intact. The thing has to live only in one head, so passing it along is what ends your private hold.
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12. What goes up every year but never comes down? Easy
Most people first say: Your height
Show answer
Your age. It only moves in one direction.
Goes up is read as rising into the sky, which sends you hunting for balloons and rockets. Take it as a number that climbs instead: every birthday adds one, and no calendar ever hands a year back.
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13. Mary's father has five daughters: Nana, Nene, Nini and Nono. What is the fifth daughter's name? Easy
Most people first say: The name Nunu
Need a hint?
The pattern Nunu is a trap.
Show answer
Mary. The first word of the riddle already told you.
Four names built on N invite you to finish the pattern, which is exactly the misdirection. The question opened with the fifth daughter's name and then buried it under a list, so read the first word again.
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14. What runs but never walks, has a mouth but never talks, and has a bed but never sleeps? Easy
Most people first say: A clock
Need a hint?
It is a feature of the landscape.
Show answer
A river. It runs its course, opens into a mouth, and rests in a riverbed.
Runs is the verb doing the work: it means flows here, not legs moving. Mouth and bed then stop being body parts and become the place a stream meets the sea and the channel it rests in.
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15. What disappears the moment you say its name? Easy
Need a hint?
You break it just by answering.
Show answer
Silence. Speaking any word at all destroys it.
Disappears makes you look for something fragile, like a bubble or a dream. The pivot is the act of speaking itself: whatever you answer, the sound of your voice has already ended the thing you were naming.
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16. What has many teeth but cannot bite? Easy
Most people first say: A zipper
Show answer
A comb. Its teeth only untangle hair.
Teeth is a borrowed word, the name for any row of thin points, and bite pulls you toward animals anyway. Look for something with a straight row of points that is dragged through hair rather than food.
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17. Six children and two dogs stood under one small umbrella, yet nobody got wet. How? Easy
Most people first say: The umbrella was huge
Need a hint?
Nobody mentioned the weather.
Show answer
It was not raining. The umbrella had nothing to block.
Six kids and two dogs under one umbrella is meant to look impossible, so you argue about size. The story never mentions rain; you added the weather yourself, and without it there was nothing to get wet from.
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18. A man lives on the tenth floor. Every morning he rides the elevator down. In the evening he rides to the seventh floor and walks the rest, unless it is raining or someone else is in the elevator. Why? Medium
Most people first say: He wants the exercise
Need a hint?
Think about what an umbrella and a stranger have in common here.
Show answer
He is very short. He can only reach the button for the seventh floor, unless he has an umbrella to press higher or someone presses it for him.
Rain and a stranger are the details to interrogate: both change what he can reach, not what he wants. Picture the button panel from below, with the seventh button as high as his arm goes and an umbrella to extend it.
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19. A man pushes his car until he reaches a hotel. The moment he arrives, he knows he is bankrupt. What happened? Medium
Most people first say: His car broke down
Need a hint?
The car fits in his hand.
Show answer
He is playing Monopoly. His token is the car, and he landed on a hotel he cannot afford.
Pushes is the word to weigh. A real car pushed to a real hotel gets you a tow, not instant bankruptcy, so the car must be small enough to move with one finger and the hotel a piece of plastic on a board.
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20. Two women order identical glasses of iced tea. One drinks hers slowly and dies. The other drinks four glasses quickly and is fine. Why? Medium
Most people first say: The tea itself was poisoned
Need a hint?
Something in the glass changed over time.
Show answer
The poison was in the ice. The fast drinker finished before her ice melted, the slow drinker gave it time to dissolve.
Identical glasses and slowly are the two facts to hold together: the drinks were the same, so the difference has to be time. Whatever was in the glass had to change while she sipped, and frozen water is the one ingredient that does.
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21. The person who makes it sells it. The person who buys it never uses it. The person who uses it never knows it. What is it? Medium
Most people first say: A gift
Need a hint?
It is a product with a very quiet customer.
Show answer
A coffin. It is built to sell, bought for someone else, and its occupant is past knowing.
Never knows is the clause that removes ordinary products: a gift is used by someone who knows exactly what it is. The buyer and the user must be different people, and the user has to be past noticing anything at all.
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22. You are downstairs with three light switches. One controls a bulb upstairs. You may go upstairs only once. How do you find the right switch? Medium
Most people first say: It cannot be done in one trip
Need a hint?
A bulb gives off more than light.
Show answer
Turn the first switch on for a few minutes, turn it off, turn the second on, then go up. A lit bulb means switch two, a warm dark bulb means switch one, a cold dark bulb means switch three.
One trip up sounds like one bit of information, and that assumption is the whole difficulty. A bulb records its own history in temperature, so touching the glass reads a switch that was flipped and shut off before you climbed.
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23. You have two ropes. Each takes exactly one hour to burn, but they burn unevenly along their length. How do you measure exactly 45 minutes? Medium
Most people first say: Fold a rope in half
Show answer
Light the first rope at both ends and the second at one end. When the first burns out, 30 minutes have passed, so light the other end of the second rope. It burns out 15 minutes later, at exactly 45 minutes.
Uneven means every mark you could measure along the rope is worthless. Time still divides cleanly: two flames eat the whole hour of fuel between them, so they meet at the half hour wherever that point happens to fall.
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24. A moving truck gets wedged tight under a low bridge. Engineers argue for an hour about cutting the bridge or unloading the trailer. A kid on a bicycle fixes it in one sentence. What does the kid say? Medium
Most people first say: Cut the truck's roof off
Need a hint?
Make the truck lower, not lighter.
Show answer
Deflate the tires. The truck drops a few centimeters and rolls out on its own.
Every adult in the story attacks the bridge or the cargo, so those are the only two levers you consider. Height is the third quantity nobody names, and the truck rests on four cushions of air that can be let down.
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25. Two girls were born to the same mother on the same day of the same year, yet they are not twins. How? Medium
Most people first say: It is impossible
Need a hint?
Maybe someone is missing from the story.
Show answer
They are two of a set of triplets. The wording never said there were only two children.
Two girls is a count of the girls in the question, not a count of the babies born that day. Add a third sibling to the same delivery and the label changes while every fact printed stays true.
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26. At two in the morning a hotel guest dials the room next to his, lets it ring once, and hangs up without saying a word. Then he finally falls asleep. Why did he call? Medium
Most people first say: A wrong number
Need a hint?
The call solved a sound problem.
Show answer
The neighbor was snoring. The ring woke him just enough to stop the noise.
Then he finally falls asleep is the clue to work from: the call solved whatever kept him awake, and a ringing phone through a wall does one thing. It jolts a sleeper just enough to change position and go quiet.
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27. Two sisters stand on the same sheet of newspaper at the same time, yet no matter how far they reach, they cannot touch each other. Where is the newspaper? Medium
Most people first say: The paper is in two pieces
Need a hint?
Something solid stands between them.
Show answer
Under a closed door. One sister stands on each end, with the door between them.
Cannot touch no matter how far they reach means something solid blocks them, yet both feet rest on one sheet. Ask what a flat sheet can pass beneath that two people cannot: a door, shut, with the paper sliding under it.
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28. A pet shop owner swears his parrot repeats every single word it hears. A week later the buyer storms back because the bird has not made a sound. The owner told the truth. How? Medium
Most people first say: The buyer never spoke to it
Need a hint?
Read the promise one word at a time.
Show answer
The parrot is deaf. It repeats every word it hears, and it hears nothing at all.
Every word it hears sounds like a guarantee of talking, yet the promise covers only sounds that reach the bird. You supplied working ears; the owner never did, and a repeat of nothing is still a repeat.
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29. A girl fell off a 20 foot ladder yet was not hurt at all. Why not? Medium
Most people first say: She landed in a haystack
Need a hint?
Where on the ladder was she standing?
Show answer
She fell off the bottom rung. The ladder was tall, her fall was not.
Twenty feet describes the ladder, not the drop, and you are the one who put her at the top. Nothing in the sentence places her above the first step, so the height quoted belongs to the equipment rather than to her.
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30. How far can a dog run into the woods? Medium
Most people first say: All the way through
Need a hint?
Think about what changes at the center.
Show answer
Halfway. After the middle it is running out of the woods, not into them.
Into is the word under strain. Running into the woods only describes the dog until it reaches the center; every stride after that carries it toward the far edge, which is running out, whatever the dog thinks.
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31. Before Mount Everest was discovered, what was the highest mountain on Earth? Medium
Most people first say: The second tallest peak
Need a hint?
Discovery changes knowledge, not geography.
Show answer
Still Mount Everest. It was the highest whether or not anyone had found it yet.
Before nudges you into history, as though the ranking waited on a survey team. A peak's altitude does not depend on anyone knowing about it, so the list of tallest mountains was the same list a century earlier.
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32. A woman shoots her husband, then holds him underwater for five minutes. An hour later they go out for a lovely dinner together. How? Medium
Most people first say: It was all a dream
Need a hint?
Every violent word here has a harmless second meaning.
Show answer
She photographed him. She shot a picture, developed the film in liquid, and hung it to dry.
Three violent words in a row make you commit to a crime scene before reading the fourth. Each one has a darkroom sense: aiming a lens, a bath of chemicals, a print pegged up to dry.
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33. A shepherd whistles for his dog from the far bank of a wide river. There is no bridge and no boat, yet the dog reaches him in under a minute without swimming and without getting wet. How? Medium
Most people first say: The river had dried up
Need a hint?
Think about the season.
Show answer
The river was frozen. The dog trotted straight across the ice.
Wide river, no bridge, no boat: the list of missing things is there to make water feel like the only surface. Nothing says the water was liquid, so give the scene a winter and the crossing becomes a walk.
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34. My aunt says she can name the score of any football match before it kicks off, and she has never once been wrong. What score does she always give? Medium
Most people first say: One nil
Need a hint?
Listen to when she makes the call.
Show answer
Nil nil. Before kickoff nobody has scored, so every match in history starts there.
Before it kicks off is the phrase that carries the trick, because the aunt is naming the score at that instant, not predicting the final. At the whistle every game in history reads the same, so she cannot miss.
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35. A rope ladder hangs over the side of a boat with its bottom rung touching the water. The tide rises half a meter every hour. After six hours, how many rungs are underwater? Medium
Most people first say: Six rungs
Need a hint?
The boat is not nailed to the seabed.
Show answer
None. The boat floats, so the ladder rises with the tide.
Half a meter every hour times six is the arithmetic you are meant to do, and it is worthless. Boat is the word to reread: it floats, so the deck, the ladder and the water climb together and the gap never changes.
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36. Poor people have it. Rich people need it. If you eat it, you die. What is it? Medium
Most people first say: Hunger or debt
Need a hint?
The answer makes all three lines true at once.
Show answer
Nothing. The poor have nothing, the rich need nothing, and eating nothing kills you.
Three lines that contradict each other are a sign the answer is not an object. Something the poor own and the rich still lack is an absence, and eating an absence is starving, which turns the last line true.
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37. A farmer builds a straight fence exactly ten meters long, with a post standing at every meter mark from the very start to the very end. How many posts does he plant? Medium
Most people first say: Ten posts
Need a hint?
Count the ends, not just the gaps.
Show answer
Eleven. Ten gaps of one meter need a post on both ends, so the posts outnumber the gaps by one.
Ten meters and a post at every meter mark invite the answer ten, which counts the gaps. The phrase from the very start to the very end is what adds one: a fence with ten spaces has a post before the first space.
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38. A window cleaner falls from a 40 story building yet walks away without a scratch. How? Medium
Most people first say: He fell onto an awning
Need a hint?
Which side of the glass was he on?
Show answer
He was cleaning windows from the inside. He fell off a small stepladder onto the floor.
Forty stories is there to make the fall enormous, and the building is where you put him on the outside. The riddle never says which side of the glass he stands on; a cleaner indoors falls two feet.
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39. Without adding, subtracting, multiplying or dividing, how do you make the number seven even? Medium
Most people first say: It cannot be done
Need a hint?
Work on the word, not the value.
Show answer
Take away the letter s. Seven turns into even.
Without adding, subtracting, multiplying or dividing lists every arithmetic move to keep you inside arithmetic. The number is also a word on the page: drop its first letter and the four that remain spell the property you wanted.
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40. A monkey, a squirrel and a parrot race to the top of a tall coconut palm. Whoever gets there first wins the banana. Who takes it? Medium
Most people first say: The monkey
Need a hint?
Check what actually grows up there.
Show answer
No one. A coconut palm has no bananas to win.
Three climbers and a prize make you rank speed, monkey first, and the race never happens. Coconut is the word that ends it: the tree named in the question grows one fruit, and it is not the fruit on offer.
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41. I am light as a feather, yet the strongest person cannot hold me for more than a few minutes. What am I? Medium
Most people first say: A soap bubble
Need a hint?
You are holding it right now, briefly.
Show answer
Breath. Holding it takes no strength, but nobody can hold it for long.
Hold is doing two jobs: the phrase about the strongest person makes you picture gripping weight, while the riddle means holding in, the way you hold a note. Lungs give out long before muscles do.
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42. A man is found hanging in a locked room with no furniture, only a puddle of water beneath his feet. How did he do it? Medium
Most people first say: He jumped from the window
Need a hint?
The puddle used to be his platform.
Show answer
He stood on a large block of ice. It melted away, leaving only the puddle.
No furniture is the detail to explain, because reaching that height needed a platform and the room holds none. The puddle is the platform's leftover: something solid that turned to water and left no object behind.
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43. A man leaves home, makes three left turns, and returns home to find two masked men waiting for him. Who are they? Medium
Most people first say: Two burglars
Need a hint?
Home is a plate, not a house.
Show answer
The catcher and the umpire. He is playing baseball and just ran the bases back to home plate.
Masked men waiting at home reads like a break in, but the three left turns are the odd detail worth trusting. A path that turns left three times and lands where it began traces a diamond, and home there is a plate.
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44. What is always in front of you but can never be seen? Medium
Show answer
The future. It is always ahead, yet invisible until it arrives.
In front of you is a place until you read it as time. Ahead in space is the whole room; ahead in time is next week, which no eye reaches, and the moment it arrives it stops being ahead.
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45. A guard tells a prisoner: say one sentence. If it is true, we take your gold. If it is false, we take your horse. The prisoner says five words and rides away with both. What did he say? Hard
Most people first say: This sentence is false
Need a hint?
Aim the sentence at the punishment itself.
Show answer
You will take my horse. If that is true they must take his gold instead, which makes it false. If it is false they must take the horse, which makes it true. The rule eats itself, so he keeps everything.
Aim the sentence at the rule itself and the rule cannot decide. Calling it true forces the gold penalty, which makes the claim false; calling it false forces the horse penalty, which makes it true, so neither outcome can be carried out.
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46. A gardener must plant four trees so that each one stands exactly the same distance from all the others. On flat ground it cannot be done. How does she manage it? Hard
Most people first say: A square
Need a hint?
Leave the flat page and think in three dimensions.
Show answer
She uses a hill. Three trees form a triangle around the base and the fourth goes on top, making a pyramid with four equal edges.
Flat ground is the assumption the riddle even names, and most solvers still keep it. Four points that are all one distance apart cannot lie on a page; they need a fourth corner lifted above the other three, which a hill provides.
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47. How many seconds are there in one whole year? Hard
Most people first say: About thirty one million
Need a hint?
Think of dates, not clocks.
Show answer
Twelve. Every month has a second: January 2nd, February 2nd, and so on through December.
Seconds is read as ticks of a clock, and the sum in your head runs into the millions. The riddle means the second day of each month, so the count is one per month across the calendar.
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48. Two doors, one leads to freedom and one to doom. Two guards know which is which, one always lies and one always tells the truth. You may ask one question. What do you ask? Hard
Most people first say: Ask which door is safe
Need a hint?
Make the lie and the truth cancel each other out.
Show answer
Ask either guard which door the other guard would say leads to freedom, then take the opposite door. Both guards end up pointing at the wrong door, so the opposite is safe.
Routing the question through the other guard puts exactly one falsehood into every reply: the honest man reports a lie, the liar spoils a truth. That is why both answers land on the same side, whichever guard you picked.
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49. A rooster sits at the very top of a slanted barn roof and lays an egg. Which side of the roof does the egg roll down? Easy
Most people first say: The lower side
Show answer
Neither. Roosters do not lay eggs.
Slanted and very top set up a physics question about which way the egg tips. Read the bird instead: a rooster is male, so the sentence describes an event that never took place and there is nothing on the roof to follow.
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50. Some months have 31 days and some have 30. How many months have 28 days? Easy
Most people first say: Only February
Show answer
All twelve. Every month contains a 28th day.
February is the month everybody names, because 28 days is its famous length. The question asks which months have 28 days, not which have exactly 28, and a 31 day month passes its 28th like every other.
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51. There are five apples in a bowl and you take away three. How many apples do you have? Easy
Most people first say: Two apples
Show answer
Three. You have the ones you took.
Take away is the phrase that starts a subtraction, and the question then swaps its subject. It never asks how many stay in the bowl; it asks what you have, and the ones in your hand are the ones you took.
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52. A man builds a house with all four walls facing south. A bear wanders past the door. What color is the bear? Easy
Most people first say: A brown bear
Show answer
White. The house sits at the North Pole, so it is a polar bear.
All four walls facing south is the geometry clue: the only spot on Earth where every direction is south is the North Pole. From there the bear's color follows from geography, because the only bears that far north are polar bears.
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53. Which weighs more, a pound of feathers or a pound of bricks? Easy
Most people first say: The bricks
Show answer
Neither. A pound is a pound.
Feathers and bricks drag your eye to size, so you compare a sack with a stack and answer from the picture. The question already fixed the quantity in both hands, leaving nothing left to compare.
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54. A farmer keeps seventeen sheep, and all but nine run off. How many sheep does he have left? Easy
Most people first say: Eight sheep
Show answer
Nine. All but nine ran away.
Seventeen sits there to be subtracted from, and the subtraction is the mistake. All but nine already reports the survivors rather than the runaways, so the second number is already the count you were asked for.
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55. Two fathers and two sons go fishing. Each catches exactly one fish, yet only three fish are caught. How? Easy
Most people first say: Four people
Show answer
There are only three people: a grandfather, his son, and his grandson.
Two plus two makes four people before you notice that one man can hold two of those labels at the same time. Count roles, not bodies: a man with a child and a parent above him fills two slots by himself.
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56. You walk into a pitch dark room holding a single match. There is a candle, an oil lamp, and a wood stove. What do you light first? Easy
Most people first say: The candle
Show answer
The match. Nothing else can be lit without it.
Candle, lamp and stove form a menu that pulls your eye to a choice, while the single match sits earlier in the sentence as a plain fact. Nothing on the list can burn before that flame exists.
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57. On an island of knights who always tell the truth and knaves who always lie, you meet A and B. A says, We are both knaves. What is each one? Hard
Most people first say: Both are knaves
Need a hint?
Could a knave ever truthfully call himself one?
Show answer
A is a knave and B is a knight.
Grade the sentence against its own speaker first, since A is one of the two people it describes. Nobody can truthfully call himself a liar, so A is lying, and a false we are both knaves leaves B on the honest side.
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58. Three friends pay ten dollars each for a thirty dollar room. The clerk refunds five dollars through a bellhop who pockets two and returns one to each guest. Each paid nine, totaling twenty seven, plus the bellhop's two makes twenty nine. Where is the missing dollar? Hard
Most people first say: The clerk kept it
Need a hint?
Add the room to the bellhop, not the guests to the bellhop.
Show answer
Nowhere. The twenty seven already includes the bellhop's two, so adding it double counts.
Twenty seven plus two is the addition the riddle performs for you, and it is the error. The guests' twenty seven already contains the bellhop's two; the honest sum is twenty five for the room plus two pocketed plus three refunded, thirty.
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59. You pick one of three doors hoping for the car. The host, who knows what hides behind each, opens a different door showing a goat, then offers to let you switch to the last door. Should you switch? Hard
Most people first say: It makes no difference
Need a hint?
Count how often your very first pick is right.
Show answer
Yes. Switching wins two times out of three.
Two closed doors look like a coin toss, and that symmetry is the premise you supplied. The host never opens the car, so his pick is steered by where it hides, and the odds your first guess missed pile onto the door he avoided.
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60. You have nine identical looking balls, but one is slightly heavier. Using a balance scale only twice, how do you find the heavy one? Hard
Most people first say: Weigh them in pairs
Need a hint?
Split the balls into three groups, not two.
Show answer
Weigh three against three; the heavier side, or the odd trio if they balance, holds it, then weigh one of those three against another.
Two pans invite you to halve the pile, and halving nine twice cannot get you there. A balance reports three outcomes, left, right or level, so it sorts a pile into thirds and level is an answer rather than a failure.
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61. Four people must cross a rickety bridge at night sharing one flashlight that lights only two crossing together, who then move at the slower one's pace. They need one, two, seven, and ten minutes. What is the fastest everyone can be across? Hard
Most people first say: Twenty one minutes
Need a hint?
The two slowest should cross together, and only once.
Show answer
Seventeen minutes.
Escorting each straggler with the quickest walker feels efficient, and it charges the ten minute pace twice. Pair the two slowest so their trip costs ten once, then let the pair of quick walkers handle every return trip.
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62. A frog sits at the bottom of a well thirty feet deep. Each day it climbs up three feet, and each night it slides back two. How many days does it take to escape? Hard
Most people first say: Thirty days
Need a hint?
Check what happens on the final morning before any slide.
Show answer
Twenty eight days.
Three up and two back invites a tidy division, thirty feet at one net foot a day. That sum assumes the frog is still in the shaft when night falls, and on the last climb it is already out in daylight.
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63. One of a thousand numbered bottles is poisoned, and a test strip turns dark a day after touching any poison. With ten strips and a single day, how do you find the poisoned bottle? Hard
Most people first say: Test ten bottles at a time
Need a hint?
Let each strip test many bottles at once.
Show answer
Number the bottles in binary, let each strip stand for one of ten bits, and test it on every bottle whose number has that bit set; the darkened strips spell the number.
Ten strips against a thousand bottles feels hopeless only while you assume a strip may touch one bottle. Let a strip sample a crowd of bottles instead and each strip answers a single yes or no question, so ten answers name one bottle.
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64. Two trains one hundred miles apart race toward each other, each at fifty miles per hour. A bird flying seventy five miles per hour darts between their fronts until they meet. How far does the bird fly? Hard
Most people first say: Add up an endless series
Need a hint?
Work out how long the bird stays in the air.
Show answer
Seventy five miles.
Darting back and forth invites you to add up shrinking legs forever, and that sum is a dead end. Ask for the clock instead: the gap closes at a hundred miles an hour, so the bird stays airborne for exactly one hour.
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65. You have a seven minute hourglass and an eleven minute hourglass. How do you measure exactly fifteen minutes? Hard
Most people first say: Run them one after another
Need a hint?
Flip a glass the moment it empties, then watch the leftover sand.
Show answer
Start both at once. When the seven empties, flip it. When the eleven empties at minute eleven, flip the seven again, and its four minutes of sand run out at minute fifteen.
Adding and subtracting seven and eleven never reaches fifteen, so the printed numbers are not the ones you get to use. Turn a glass over the instant it empties and it hands you the leftover of the other one as a new interval.
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66. A farmer must ferry a wolf, a goat, and a cabbage across a river in a boat that carries only him and one of them. Left alone, the wolf eats the goat and the goat eats the cabbage. In what order does he cross? Hard
Most people first say: Take the wolf first
Need a hint?
Something has to make a return trip.
Show answer
Take the goat over, return empty, take the wolf, bring the goat back, take the cabbage, return empty, then take the goat.
Sort the three by who can sit next to whom: the wolf ignores the cabbage, so that pair is safe unattended, while the goat is unsafe beside either one. That single fact forces the goat to ride back on the middle trip.
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67. On the island of knights and knaves, A tells you, If I am a knight, then B is a knight. What are A and B? Hard
Most people first say: Both are knaves
Need a hint?
Ask what an if statement is worth coming from a liar.
Show answer
Both are knights.
An if sentence counts as true whenever its if half is false, and that is the pivot a liar cannot survive. Were A a knave, his conditional would come out true, which knaves are not allowed, so A speaks honestly and B follows.
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68. At a small gathering every person shakes hands with every other person exactly once, producing sixty six handshakes in all. How many people were there? Hard
Most people first say: Thirty three people
Need a hint?
Two people share every handshake you count.
Show answer
Twelve.
Sixty six invites a quick division, and it misses because a handshake belongs to two people at once. Count the pairs a group can form, then halve that to cancel the double count, and the guest list is pinned.
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69. A father is four times as old as his son. In twenty years he will be only twice his son's age. How old are they now? Hard
Most people first say: Eighty and twenty
Need a hint?
Both of them get twenty years older, not just the son.
Show answer
The father is forty and the son is ten.
In twenty years applies to both people, and the usual slip is ageing only the son. With the son at one share and the father at four, adding twenty to each leaves the father at double only when a share is ten.
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70. The day before yesterday I was twenty five, yet next year I will turn twenty eight. On what day are we speaking? Hard
Most people first say: It cannot happen
Need a hint?
Two days ago can belong to last year.
Show answer
January the first, with a birthday on December the thirty first.
Those two days hold just two of the four ages, twenty five and twenty six. The pivot is the year boundary between them: a birthday on the final day leaves twenty seven for this December and twenty eight for the next.
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71. With only a three liter jug, a five liter jug, and a running tap, how do you measure exactly four liters? Hard
Most people first say: Pour one liter out of the five
Need a hint?
The small jug's empty space is your ruler.
Show answer
Fill the five and pour into the three, leaving two; empty the three and move the two into it; refill the five and top off the three, which leaves four in the five.
Neither jug is marked at four, so the measuring tool has to be built. Leave a gap on purpose: a jug already holding two has room for exactly one more, and drawing that liter off the full five sets the remainder.
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72. Blindfolded, you face ten coins on a table and are told exactly three show heads. You cannot see or feel which. How do you split them into two piles that each show the same number of heads? Hard
Most people first say: It cannot be done blindfolded
Need a hint?
Flip every coin in one of the piles.
Show answer
Slide any three coins into a separate pile and flip all three; now both piles show equal heads.
Being unable to identify a single coin feels like a blocker, and that is the premise to drop. Take any three aside and flipping them turns however many heads they held into the exact number still sitting on the table.
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73. A teacher puts a black or white hat on Ann and on Ben, tells them at least one hat is black, and lets each see only the other's. She asks Ann if she knows her own color; Ann says no. Ben instantly says he knows his. What color is Ben's hat? Hard
Most people first say: Could be either color
Need a hint?
Ann saying no is information, not a shrug.
Show answer
Black.
A no sounds like a dead end, and treating it as empty is the premise to drop. What Ann fails to see is the clue: had Ben's hat been white, the teacher's at least one black would have settled Ann's own instantly.
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74. A woman says her three daughters' ages multiply to thirty six and add up to the number on the house across the street. The visitor looks and says that is not enough, so she adds, my eldest is learning piano. Now he knows. What are the ages? Hard
Most people first say: One, six and six
Need a hint?
Two age sets share a sum, and one has no single eldest.
Show answer
Two, two, and nine.
Not enough is the line doing the work: a visitor reading the house number would be finished unless two age sets shared that total. Both 1, 6, 6 and 2, 2, 9 add to thirteen, and a single eldest rules out the twin sixes.
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75. A family has exactly two children, and you learn that at least one of them is a boy. What is the chance that both children are boys? Hard
Most people first say: One in two
Need a hint?
List every boy and girl order, then cross out the impossible.
Show answer
One in three.
At least one hides which child is meant, so you cannot label a first or second boy. Keep the order in the list and three arrangements survive the news, only one of which has two sons.
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76. A knockout tennis tournament starts with sixty four players, and every match sends the loser home. How many matches decide the champion? Hard
Most people first say: Sixty four matches
Need a hint?
Count the losers, not the rounds.
Show answer
Sixty three.
A field of sixty four pulls you into drawing rounds and adding thirty two plus sixteen plus eight. Look at the losers instead: one match removes one player, and all but the winner have to be removed, so the tally follows.
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77. Three sages each receive a red hat, though each is told only that the hats are red or blue and at least one is red. Each sees the other two but not his own. After a shared pause in which no one speaks, all three announce red at once. How? Hard
Most people first say: A lucky shared guess
Need a hint?
Imagine one hat blue and ask who would speak first.
Show answer
Each reasons that a blue hat would let another sage deduce his color sooner, so the silence proves every hat is red.
Silence reads as nothing happening, which is the premise to throw out. Each quiet moment eliminates the arrangements in which somebody would already have spoken, and once no blue arrangement survives that filter, every sage can name his own color.
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78. A man wills seventeen camels to his sons: half to the eldest, a third to the middle, and a ninth to the youngest. A neighbor lends one camel to make eighteen. How does the herd then divide? Hard
Most people first say: Eight and a half camels
Need a hint?
Add a half, a third and a ninth before dividing anything.
Show answer
Nine, six, and two, which total seventeen, so the neighbor takes his own camel back.
Add the fractions before dividing anything: a half, a third and a ninth come to seventeen eighteenths, not a whole herd. The will never used up every animal, so a loan of one makes each share whole and still goes home.
Classic logic riddles with answers
The elevator man and the dog in the woods both live here. Old puzzles, still undefeated.
Logic riddles for beginners
Some resolve in one clean step. Start anywhere, since every clue you need sits inside the question.
Deduction puzzles with hints
63 of the 78 carry a hint. Open one when you stall, then go back to the question with the extra fact.
Your score
FAQ about Logic Riddles with Answers
What is a logic riddle?
A short scene or rule set where every fact you need is printed and the answer follows from reading it exactly. The difficulty comes from a premise you supply yourself, such as assuming a surgeon is a man, or from a case you have not tested yet, such as what a liar's conditional statement is worth.
How do you solve logic riddles?
Write the fact your first answer depends on as a plain sentence, then reread the riddle looking for it. If the riddle never said it, drop it and read the scene without it. On the deduction puzzles, pick one case, follow it until it contradicts a stated rule, and cross it off.
What is the difference between a logic riddle and a lateral thinking puzzle?
A logic riddle can be settled in one line once the hidden premise is named, like the rooster that lays no egg or the boat that rises with the tide. A lateral thinking puzzle hides more of the story, so a group usually needs several yes or no questions before the scene makes sense.
The one-line habit from this page, name the premise and test it, is the same move the hard riddles demand under a second layer of wordplay. The long riddles run the same classics at story length, so the line you have to test hides inside the plot instead of sitting in plain view.