Logic Riddles with Answers

He fell from a plane. The package was his parachute, and it never opened.

The unopened package is a parachute that failed, so he fell from a plane.

They were goldfish. The cat knocked their bowl off the table and they suffocated.

The broken glass is a fishbowl, so Romeo and Juliet are fish that suffocated.

The surgeon is his mother. The riddle only works if you assume surgeons are men.

Drop the assumption that surgeons are men; the surgeon is the boy's mother.

His horse is named Friday. He rode in and out on the same animal, not the same weekday.

Friday is the horse's name, not the day, so he rides in and out on Friday.

He is walking. The rule applies to driving, and he left his truck behind.

One-way rules govern driving, and he is on foot, so he breaks nothing.

Nowhere. You do not bury survivors, they are alive.

Survivors are alive, so there is no one to bury.

There is no smoke. Electric trains do not burn anything.

An electric train burns no fuel, so there is no smoke to drift at all.

A promise. Breaking it needs no hands at all.

A promise is abstract, so breaking it needs no physical contact.

He is bald. There was no hair to get wet.

He is bald, so the rain finds no hair to wet.

Fire. Fuel makes it bigger, water puts it out.

Fuel feeds fire and water kills it, matching grow and die.

A secret. Telling it is exactly what destroys it.

Sharing a secret is the very act that ends your sole hold on it.

Your age. It only moves in one direction.

Age only climbs each year and never falls back.

Mary. The first word of the riddle already told you.

The first word names Mary, who is the fifth daughter.

A river. It runs its course, opens into a mouth, and rests in a riverbed.

A river runs, has a mouth, and lies in a bed, matching each clue.

Silence. Speaking any word at all destroys it.

Naming silence requires speaking, which destroys the silence.

A comb. Its teeth only untangle hair.

A comb's teeth only groom hair and cannot bite.

It was not raining. The umbrella had nothing to block.

It was not raining, so the umbrella had nothing to block.

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.

He is too short to reach past the seventh button; an umbrella or another rider presses the rest.

He is playing Monopoly. His token is the car, and he landed on a hotel he cannot afford.

The car is a game token, so landing on an unaffordable hotel bankrupts him in Monopoly.

The poison was in the ice. The fast drinker finished before her ice melted, the slow drinker gave it time to dissolve.

The poison hides in the ice, so only the slow drinker waited long enough for it to melt in.

A coffin. It is built to sell, bought for someone else, and its occupant is past knowing.

Only a coffin is made to sell, bought for another, and used by someone past knowing.

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.

Use the bulb's heat; a warm dark bulb was the switch turned on earlier.

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.

Burning a rope from both ends halves its time, giving 30 then 15 minutes.

Deflate the tires. The truck drops a few centimeters and rolls out on its own.

Deflating the tires lowers the truck enough to roll free of the bridge.

They are two of a set of triplets. The wording never said there were only two children.

Three born together are not twins, and nothing limited the count to two.

The neighbor was snoring. The ring woke him just enough to stop the noise.

The single ring wakes the snoring neighbor just enough to stop the noise.

Under a closed door. One sister stands on each end, with the door between them.

A closed door separates them while each stands on an end of the same sheet.

The parrot is deaf. It repeats every word it hears, and it hears nothing at all.

It repeats every word it hears, and being deaf it hears none.

She fell off the bottom rung. The ladder was tall, her fall was not.

The ladder is tall, but she fell from its lowest rung, barely any drop.

Halfway. After the middle it is running out of the woods, not into them.

Past the midpoint the dog is running out of the woods, not in.

Still Mount Everest. It was the highest whether or not anyone had found it yet.

Everest was already tallest; being discovered does not change its height.

She photographed him. She shot a picture, developed the film in liquid, and hung it to dry.

Shoot means photograph and the water is developing fluid, not violence.

The river was frozen. The dog trotted straight across the ice.

The river is frozen, so the dog trots across the ice dry.

Nil nil. Before kickoff nobody has scored, so every match in history starts there.

Every match starts scoreless before kickoff, so nil-nil is always right.

None. The boat floats, so the ladder rises with the tide.

The boat floats up with the tide, so the ladder never sinks deeper.

Nothing. The poor have nothing, the rich need nothing, and eating nothing kills you.

Nothing fits all three: the poor have it, the rich need it, eating it kills.

Eleven. Ten gaps of one meter need a post on both ends, so the posts outnumber the gaps by one.

Ten one-meter gaps need a post at both ends, one more post than gaps.

He was cleaning windows from the inside. He fell off a small stepladder onto the floor.

He cleaned from inside, falling only off a stepladder to the floor.

Take away the letter s. Seven turns into even.

Deleting the letter s turns the word seven into even.

No one. A coconut palm has no bananas to win.

A coconut palm grows no bananas, so there is no prize to win.

Breath. Holding it takes no strength, but nobody can hold it for long.

Breath weighs nothing yet nobody can hold it more than minutes.

He stood on a large block of ice. It melted away, leaving only the puddle.

He stood on a block of ice that melted into the puddle below.

The catcher and the umpire. He is playing baseball and just ran the bases back to home plate.

Three left turns round the bases bring him home to the catcher and umpire.

The future. It is always ahead, yet invisible until it arrives.

The future always lies ahead yet stays unseen until it arrives.

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.

The sentence is true only if false and false only if true, so no rule can apply.

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.

Putting the fourth tree atop a hill forms a pyramid with four equal edges.

Twelve. Every month has a second: January 2nd, February 2nd, and so on through December.

Each month has a 2nd, so a year holds twelve of those seconds.

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.

Asking what the other guard would say always yields the wrong door, so choose the opposite.

Neither. Roosters do not lay eggs.

Only hens lay eggs, so a rooster produces nothing to roll down either side.

All twelve. Every month contains a 28th day.

Every month has at least 28 days, so all twelve of them qualify.

Three. You have the ones you took.

The question asks what you now hold, and you took three of the apples.

White. The house sits at the North Pole, so it is a polar bear.

Only at the North Pole can all four walls face south, where the bears are white.

Neither. A pound is a pound.

Both are measured at exactly one pound, so their weights are equal.

Nine. All but nine ran away.

The phrase all but nine means that nine sheep stayed behind.

Once. After that you are subtracting from twenty.

After the first subtraction the number is no longer twenty five.

There are only three people: a grandfather, his son, and his grandson.

The middle man is both a father and a son, so three people fill both roles.

The match. Nothing else can be lit without it.

The match is the only flame available, so it has to be lit before anything else.

A is a knave and B is a knight.

If A told the truth he would be a knave, which is impossible, so A lies; both being knaves is therefore false, and since A is a knave, B must be a knight.

Nowhere. The twenty seven already includes the bellhop's two, so adding it double counts.

The guests' twenty seven splits into twenty five for the room and two for the bellhop, so nothing is missing.

Yes. Switching wins two times out of three.

Your first pick is right only one third of the time, so the remaining door holds the car the other two thirds.

Weigh three against three; the heavier side, or the odd trio if they balance, holds it, then weigh one of those three against another.

Each weighing narrows nine to three and then three to one, since a balance always tips toward the heavier group.

Seventeen minutes.

Send the one and two first, run the light back with the one, send the seven and ten together, return the two, then cross the one and two.

Twenty eight days.

It nets one foot a day until day twenty eight, when it starts at twenty seven and climbs the last three feet out before it can slip.

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 binary digits can label more than a thousand bottles, so the pattern of dark strips names exactly one.

Seventy five miles.

The trains meet in exactly one hour, and the bird flies seventy five miles per hour for that whole hour.

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.

At minute eleven the just flipped seven glass holds four minutes of sand, which finishes precisely at fifteen.

Take the goat over, return empty, take the wolf, bring the goat back, take the cabbage, return empty, then take the goat.

Shuttling the goat back on the middle trip keeps the wolf and cabbage, safe together, from ever guarding it alone.

Both are knights.

A knave's words would have to be false, but that conditional is true whenever A is a knave, so A must be a knight, and his true statement then makes B a knight too.

Twelve.

Handshakes equal n times n minus one over two, and only twelve gives sixty six.

The father is forty and the son is ten.

Father equals four times son, and father plus twenty equals twice son plus twenty, which solves to forty and ten.

January the first, with a birthday on December the thirty first.

On December 31 the speaker turned 26, so this year brings 27 and next year 28, while two days ago they were still 25.

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.

Topping off the three liter jug that already holds two draws exactly one liter from the full five, leaving four.

Slide any three coins into a separate pile and flip all three; now both piles show equal heads.

If the grabbed pile held h heads, flipping its three coins leaves three minus h heads, matching the three minus h left behind.

Black.

If Ann had seen a white hat she would know her own was black, so her uncertainty proves Ben's hat is black.

Two, two, and nine.

Only the age sets 1, 6, 6 and 2, 2, 9 share a sum, thirteen, and naming a single eldest rules out the pair of sixes.

One in three.

The equally likely cases boy boy, boy girl, and girl boy remain, and only one of the three is two boys.

Sixty three.

Every match eliminates exactly one player, and sixty three must lose for a single champion to remain.

Each reasons that a blue hat would let another sage deduce his color sooner, so the silence proves every hat is red.

A single blue hat would give someone a faster deduction, so the shared silence rules out any blue and leaves all red.

Nine, six, and two, which total seventeen, so the neighbor takes his own camel back.

Eighteen splits cleanly into nine, six, and two, and since those add to seventeen the borrowed camel is left over.