Logic Riddles

Ten logic riddles and answers: work each one out, then tap Show answer to check the reasoning.

Logic Riddles

Four dogs step on a scale one at a time, and no two weigh the same. Tig is the lightest. Ursa is heavier than Spot. Ursa is not the heaviest. Which dog is the heaviest?
Three cups stand in a row: left, middle and right. One holds milk, one juice and one water. The juice is not in the left cup. The water is somewhere to the right of the juice. What is in the left cup?
Five lockers are numbered 1 to 5, and a trophy is in one of them. The notes on the doors read, in order: "It is in a locker with a higher number than this one." "It is in locker 1 or locker 5." "It is in an even-numbered locker." "It is in here." "It is in locker 3." Only one of the five notes is true. Which locker holds the trophy?
Grandma Rosa has two daughters and no other children. Each daughter has two sons and no other children. How many first cousins does each of the grandsons have?
Sana, Theo and Uli each brought one dish to a picnic: a salad, a loaf of bread and a pie. They arrived one at a time. Uli brought the salad. Whoever brought the pie arrived first. Theo arrived some time after Sana. Who brought the bread?
Five jars hold marbles. In four jars every marble weighs 10 grams; in one jar every marble weighs 11 grams. You may read a kitchen scale once. How do you find the jar of heavy marbles?
What number comes next? 1, 4, 3, 6, 5, 8, and then?
Nia's brother has a daughter, Zoe. Zoe's mother has a mother-in-law. What is that mother-in-law to Nia?
Pia, Quin, Rob and Sal each have a music lesson on a different day from Monday to Thursday. Pia's lesson is the day after Quin's. Rob's lesson is earlier in the week than Quin's, but not on Monday. On which day is Sal's lesson?
What number comes next? 2, 3, 5, 7, 11, 13, and then?

Next step Crack a secret code Story riddles solved by asking

How it works

These logic riddles are deduction puzzles: the clues leave exactly one answer, and no trick or wordplay hides it. Logical riddles of five kinds are here, from a fibbing parrot to four hikers and one lantern.

Read the full guide

Problem solving riddles for a table or a team

The menu under the button keeps one kind. Weighing, pouring and crossing and Who owns what suit a group: read the riddle aloud, let people argue, and write the clues down. Truth-tellers and liars and Family relations are quicker to pose one to one. What comes next and odd one out takes a pencil.

Check the reasoning

Tap Show answer under a riddle. The answer comes first, then the deduction in order, so a wrong guess can be traced to the step where it left the clues. Show all answers opens every cover at once.

Tips

Stuck on who did it? Suppose each suspect in turn and count how many statements come out true.
Print gives the riddles with a line under each and the answers on a page of their own.

Questions and answers

What are some logic riddles with answers?

Two short ones. Jon is taller than Kay but shorter than Lee, and Mo is taller than Lee: who is second tallest? Lee. Two pears balance a mango, and a mango and a pear balance six plums: how many plums balance a pear? Two.

Are there easy logic riddles here?

Yes. About a third of the list is marked Easy: three clues, three people or one step. Choose More filters in the menu under the button, then Level. The levels are the editors' judgment.

What is the difference between logic puzzles and riddles?

A riddle usually hides its answer behind wordplay or a misleading picture. A logic puzzle states clues that leave one answer and asks you to prove it. Everything on this page is the second kind, kept short enough to read aloud.

Why are these called critical thinking riddles?

Because each one is solved by testing what the clues allow and ruling out the rest, not by recalling trivia. The reasoning under each answer shows which cases were ruled out and why.

All 100 riddles

Truth-tellers and liars 20

A marble is under one of three cups. The red cup says: "The marble is under the blue cup." The blue cup says: "The marble is not under the green cup." The green cup says: "The marble is not under me." Only one of the three notes is false. Which cup hides the marble? Answer: The red cup. Try each case. If it were under the red cup, two would be true. If it were under the blue cup, three would be true. If it were under the green cup, none would be true. Only the red cup leaves exactly one false.
A mountain goat named Pim tells the truth on Mondays, Wednesdays and Fridays and fibs on the other four days. Today Pim says: "Yesterday I told the truth." What day is it? Answer: Sunday. Pim never has two truthful days in a row, so on a truthful day the sentence would be false. Today is a fibbing day, and the sentence is false: yesterday was a fibbing day too. The only fibbing day that follows another is Sunday, after Saturday.
A paper plane lands on the teacher's desk. Dara says: "Eli threw it." Eli says: "Gus threw it." Flo says: "I did not throw it." Gus says: "Eli is wrong about me." Only one of the four statements is true. Who threw the plane? Answer: Flo. Try each case. If it was Dara, two would be true. If it was Eli, three would be true. If it was Flo, one would be true. If it was Gus, two would be true. Only Flo leaves exactly one true.
A relay team of four ran one lap each, and one runner dropped the baton. Jo says: "Kai or Lou dropped it." Kai says: "I held on to it." Lou says: "Jo did not drop it." Mo says: "Lou dropped it." Only one of the four statements is true. Who dropped the baton? Answer: Jo. Try each case. If it was Jo, one would be true. If it was Kai, two would be true. If it was Lou, four would be true. If it was Mo, two would be true. Only Jo leaves exactly one true.
An owl tells the truth on Tuesdays, Thursdays, Saturdays and Sundays and fibs on Mondays, Wednesdays and Fridays. Today the owl hoots: "Tomorrow I will tell the truth." What day is it? Answer: Saturday. Every fibbing day is followed by a truthful day, so on a fibbing day the sentence would be true, and a fibber cannot say a true thing. Today is a truthful day with another truthful day after it: Saturday, before Sunday.
Five lockers are numbered 1 to 5, and a trophy is in one of them. The notes on the doors read, in order: "It is in a locker with a higher number than this one." "It is in locker 1 or locker 5." "It is in an even-numbered locker." "It is in here." "It is in locker 3." Only one of the five notes is true. Which locker holds the trophy? Answer: Locker 1. Try each case. If it were in locker 1, one would be true. If it were in locker 2, two would be true. If it were in locker 3, two would be true. If it were in locker 4, three would be true. If it were in locker 5, two would be true. Only locker 1 leaves exactly one true.
Five neighbors each say something about who picked the last ripe plum from the tree. Ada: "It was a neighbor whose name starts with a vowel." Bo: "It was not Ada." Cleo: "It was Bo or Dev." Dev: "It was not me." Eve: "It was Cleo or me." Only one of the five statements is false. Who picked the plum? Answer: Eve. Try each case. If it was Ada, two would be true. If it was Bo, three would be true. If it was Cleo, three would be true. If it was Dev, two would be true. If it was Eve, four would be true. Only Eve leaves exactly one false.
Four doors stand in a row, and a prize waits behind one. Door 1 says: "The prize is behind door 2 or door 3." Door 2 says: "The prize is behind an odd-numbered door." Door 3 says: "The prize is not here." Door 4 says: "The prize is behind door 1." Only one of the four signs is true. Which door hides the prize? Answer: Door 4. Try each case. If it were behind door 1, three would be true. If it were behind door 2, two would be true. If it were behind door 3, two would be true. If it were behind door 4, one would be true. Only door 4 leaves exactly one true.
Four ferry pilots each always tell the truth or always fib. North says: "West is a fibber." South says: "North and East are the same kind." East says: "South is a truth-teller." West says: "Exactly one of us four is a truth-teller." Who is the only fibber? Answer: West. East vouches for South, so East and South are the same kind. If both fib, South's line is false, so North is truthful and West fibs; then North is the only truth-teller and West's line would be true. That cannot be. So East and South are truthful, North matches East and is truthful, and West, whom North calls a fibber, is the fibber.
Four friends share a tent, and one of them forgot to zip it. Nell says: "It was Omar or Rae." Omar says: "It was not me." Pia says: "It was Nell or Omar." Rae says: "It was not Pia." Only one of the four statements is true. Who forgot to zip it? Answer: Pia. Try each case. If it was Nell, three would be true. If it was Omar, three would be true. If it was Pia, one would be true. If it was Rae, three would be true. Only Pia leaves exactly one true.
In the village of Yes-and-No, every villager either always tells the truth or always fibs. You meet two of them at the well. The first one says: "Both of us are fibbers." What is each of them? Answer: The first is a fibber and the second tells the truth. A truth-teller could never say "both of us are fibbers", so the first one fibs. Then the sentence is false, so they are not both fibbers: the second tells the truth.
One of five bakers put salt in the sugar jar. Abe says: "It was Bea or Cal." Bea says: "It was not me, and it was not Dot." Cal says: "It was Edd." Dot says: "It was not Abe." Edd says: "Cal has the wrong baker." Only one of the five statements is false. Who put salt in the jar? Answer: Cal. Try each case. If it was Abe, two would be true. If it was Bea, three would be true. If it was Cal, four would be true. If it was Dot, two would be true. If it was Edd, three would be true. Only Cal leaves exactly one false.
One of four cousins hid Grandpa's slippers. Tess says: "It was Uma or Vic." Uma says: "It was not me." Vic says: "It was Will." Will says: "Vic is fibbing." Only one of the four statements is false. Who hid the slippers? Answer: Vic. Try each case. If it was Tess, two would be true. If it was Uma, two would be true. If it was Vic, three would be true. If it was Will, two would be true. Only Vic leaves exactly one false.
One of three brothers left the garden gate open. Hal says: "Kit left it open." Ian says: "Not me." Kit says: "Hal did it." Every one of the three statements is false. Who left the gate open? Answer: Ian. Try each case. If it was Hal, two would be true. If it was Ian, none would be true. If it was Kit, two would be true. Only Ian leaves none true.
One of three tins holds the tea. The tall tin is labeled: "The round tin's label is true." The round tin is labeled: "The tea is in the square tin." The square tin is labeled: "The tea is not in here." Only one of the three labels is false. Which tin holds the tea? Answer: The square tin. Try each case. If it were in the tall tin, one would be true. If it were in the round tin, one would be true. If it were in the square tin, two would be true. Only the square tin leaves exactly one false.
Somebody finished the orange juice. Ana says: "It was not me." Ben says: "It was Ana." Cy says: "It was Ben." Only one of the three statements is false. Who finished the juice? Answer: Ben. Try each case. If it was Ana, one would be true. If it was Ben, two would be true. If it was Cy, one would be true. Only Ben leaves exactly one false.
Three gardeners each always tell the truth or always fib. Ash says: "Birch and Cedar are both fibbers." Birch says: "Ash is a fibber." Cedar says: "Birch is a fibber." Exactly one of the three is truthful. Who is it? Answer: Birch. Suppose Ash is truthful. Then Birch and Cedar both fib, yet Cedar's line "Birch is a fibber" would be true. That cannot be, so Ash fibs. Then Birch's line is true, so Birch is truthful, and Cedar, who calls Birch a fibber, fibs.
Three lighthouse keepers each always tell the truth or always fib. The first says: "The second keeper and I are different kinds." The second says: "The third keeper is a fibber." The third says: "The first keeper tells the truth." Which keeper is the fibber? Answer: The second. A truthful first keeper would be right that the second is a different kind, a fibber. A fibbing first keeper would be wrong, so the second would be the same kind, a fibber again. Either way the second fibs. So the third is no fibber, and the third vouches for the first.
Three lunch boxes sit on a shelf, and one holds a cookie. The label on box 1 says: "The cookie is not in box 3." Box 2 says: "The cookie is in box 1 or box 3." Box 3 says: "The cookie is not in here." Only one of the three labels is true. Which box holds the cookie? Answer: Box 3. Try each case. If the cookie were in box 1, three would be true. If the cookie were in box 2, two would be true. If the cookie were in box 3, one would be true. Only box 3 leaves exactly one true.
Two parrots, Mango and Kiwi, each either always tell the truth or always fib. Mango squawks: "Kiwi is a fibber." Kiwi squawks: "Mango and I are the same kind." Which parrot tells the truth? Answer: Mango. If Kiwi were truthful, the two would be the same kind, so Mango would be truthful too, and Mango says Kiwi fibs. That cannot be. So Kiwi fibs, the two are different kinds, and Mango is the truthful one.

Who owns what 20

Abe, Bex, Cam, Dia and Eli each ordered a different soup: tomato, lentil, corn, mushroom and noodle. Cam ordered mushroom. Abe ordered neither tomato nor lentil. Bex ordered none of tomato, lentil or corn. Dia did not order tomato. Who ordered the tomato soup? Answer: Eli. Cam has mushroom. Bex is left with noodle only. Abe cannot have tomato or lentil, and mushroom and noodle are gone, so Abe has corn. Tomato and lentil remain for Dia and Eli, and Dia did not order tomato. So Eli did.
Ali, Bea, Cruz and Dee are 6, 7, 8 and 9 years old, each a different age. Cruz is the oldest. Bea is older than Ali. Dee is exactly one year older than Bea. How old is Ali? Answer: 6. Cruz is 9, which leaves 6, 7 and 8. Dee is one year above Bea, and Bea is above Ali, so the three go Ali, Bea, Dee from youngest up: 6, 7 and 8. Ali is 6.
Five cards numbered 1 to 5 lie face down in a row. The 3 is at the right end, and the 5 is right next to it. The 1 lies directly to the left of the 4. The 2 lies somewhere to the left of the 1. Which card is in the middle? Answer: 4. The 3 is fifth and the 5 fourth. The first three places hold 1, 2 and 4. The 1 is directly left of the 4, and the 2 is left of the 1, so they read 2, 1, 4. The middle card is the 4.
Five families live in a five-floor building, one on each floor. The Singhs live on the top floor. The Quinns live on an even-numbered floor, and the Reyes family lives directly below them. The Ortiz family lives above the Patels, and the Patels do not live on floor 1. Which floor do the Patels live on? Answer: 3. The Singhs have floor 5. If the Quinns had floor 4, the Reyes family would have floor 3, leaving floors 1 and 2, and the Patels, below the Ortiz family, would be on floor 1. That is ruled out. So the Quinns have floor 2 and the Reyes family floor 1. Floors 3 and 4 remain: the Patels on 3, the Ortiz family on 4.
Five friends line up for a photo. Uma stands at the left end. Vik stands exactly in the middle. Wes stands directly to the right of Vik. Xia is not next to Uma. The fifth friend is Yan. Who stands next to Uma? Answer: Yan. Uma is first, Vik third and Wes fourth. The second and fifth places are left for Xia and Yan. Xia cannot be next to Uma, so Xia is fifth and Yan is second, beside Uma.
Five talks at a science fair follow one another: bats, comets, deserts, eels and fossils. Comets comes right after bats. Deserts is neither first nor last. Eels comes exactly two talks after deserts. Fossils comes some time after comets. Which talk is fourth? Answer: Fossils. Deserts and eels are second and fourth, or third and fifth. Second and fourth leave first, third and fifth, with no two places in a row for bats and comets. So deserts is third and eels fifth. Bats and comets take first and second, and fossils, after comets, is fourth.
Four books lie in a stack: red, green, blue and yellow. The blue book is on top. The green book is directly under the red one. The yellow book is not at the bottom. Which book is at the bottom? Answer: Green. Blue is first. Red and green take two places in a row below it: second and third, or third and fourth. Second and third would push yellow to the bottom, which is ruled out. So yellow is second, red third and green at the bottom.
Four cars are parked in a row. The black car is at the far right. The green car is somewhere to the left of the white car. The silver car is parked between the green car and the white car. Which car is second from the left? Answer: Silver. Black takes the fourth space, so green, silver and white share the first three. Silver is between the other two and green is left of white: green, silver, white. Silver is second.
Four dogs step on a scale one at a time, and no two weigh the same. Tig is the lightest. Ursa is heavier than Spot. Ursa is not the heaviest. Which dog is the heaviest? Answer: Rex. Rule the others out. Tig is the lightest. Spot is lighter than Ursa. Ursa is not the heaviest, the last clue says. Only Rex is left.
Four lockers in a row are numbered 1 to 4 and belong to Ty, Una, Val and Wyn. Val's locker is right next to Wyn's and right next to Ty's. Ty's locker has a higher number than Una's. Which number is Val's locker? Answer: 3. Val is next to both Wyn and Ty, so those three stand side by side with Val in the middle, and Una is at one end. Ty is higher than Una, so Una cannot be locker 4: Una is locker 1. The other three fill 2, 3 and 4 with Val in the middle, which is 3. The clues do not say which of Wyn and Ty has 2 or 4.
In a spelling bee, no two children spelled the same number of words. Dov spelled more words than Esi but fewer than Fay. Gil spelled fewer than Esi. Han spelled more than Dov but fewer than Fay. Who finished third? Answer: Dov. Fay is above Dov, and Dov is above Esi. Gil is below Esi. Han fits between Dov and Fay. From the top: Fay, Han, Dov, Esi, Gil. Dov is third.
Jon is taller than Kay but shorter than Lee. Mo is taller than Lee. No two of the four are the same height. Who is the second tallest? Answer: Lee. The first sentence gives Lee above Jon above Kay. Mo is above Lee. From the tallest down: Mo, Lee, Jon, Kay. Lee is second.
Kim, Lars, Mina and Otto each play one instrument, all different: drums, flute, guitar and violin. Mina plays the guitar. Lars plays neither the drums nor the flute. Kim does not play the drums. Who plays the drums? Answer: Otto. Mina has the guitar. Lars cannot have drums or flute, and the guitar is gone, so Lars has the violin. Kim is left with drums or flute and does not play drums, so Kim has the flute. The drums are Otto's.
Lena, Max and Noor ran a race with no ties. Lena was not last. Max crossed the line right behind Noor. Who won? Answer: Lena. Max was right behind Noor, so they were first and second or second and third. First and second would leave Lena last, which is ruled out. So Noor was second, Max third and Lena first.
Lia, Moe and Nan each have one pet (a cat, a dog and a rabbit) and one favorite fruit (apples, bananas and cherries). The dog's owner likes bananas best. Lia likes apples best. Nan does not like cherries best. Moe does not own the cat. Who owns the rabbit? Answer: Moe. Lia likes apples, and Nan does not like cherries, so Nan likes bananas and Moe likes cherries. The dog belongs to the banana fan, Nan. Moe does not own the cat and the dog is taken, so Moe owns the rabbit.
Oz, Paz, Quy and Raj swam one length of the pool, with no ties. Oz touched the wall before Paz. Quy touched after Raj but before Oz. Who finished last? Answer: Paz. Raj was ahead of Quy, and Quy was ahead of Oz. Oz was ahead of Paz. The order is Raj, Quy, Oz, Paz, so Paz was last.
Pia, Quin, Rob and Sal each have a music lesson on a different day from Monday to Thursday. Pia's lesson is the day after Quin's. Rob's lesson is earlier in the week than Quin's, but not on Monday. On which day is Sal's lesson? Answer: Monday. Rob is before Quin and not on Monday, so Rob is on Tuesday at the earliest and Quin on Wednesday at the earliest. Pia comes the day after Quin, so Quin is Wednesday and Pia Thursday. Rob is Tuesday. Monday is left for Sal.
Sana, Theo and Uli each brought one dish to a picnic: a salad, a loaf of bread and a pie. They arrived one at a time. Uli brought the salad. Whoever brought the pie arrived first. Theo arrived some time after Sana. Who brought the bread? Answer: Theo. Uli has the salad, so the pie came with Sana or Theo. The pie arrived first, and Theo arrived after Sana, so Theo was not first. Sana brought the pie, and the bread is Theo's.
Three cats, Pepper, Suki and Tom, each nap in a different spot: the sofa, the rug and the windowsill. Pepper never naps on the rug. Tom is not on the sofa or the rug. Where is Suki? Answer: The rug. Tom has only the windowsill left. Pepper is not on the rug and the windowsill is taken, so Pepper has the sofa. That leaves the rug for Suki.
Three cups stand in a row: left, middle and right. One holds milk, one juice and one water. The juice is not in the left cup. The water is somewhere to the right of the juice. What is in the left cup? Answer: Milk. The water is to the right of the juice, so the juice is not in the right cup. It is not in the left cup either, so it is in the middle, and the water is on the right. The left cup holds the milk.

Family relations 20

A grandmother, her daughter and her granddaughter stand in a photo. The daughter is exactly twice as old as the granddaughter, and the grandmother is exactly twice as old as the daughter. Their three ages add up to 98. How old is the daughter? Answer: 28. Call the granddaughter's age one share. The daughter is two shares and the grandmother four, which makes seven shares. 98 divided by 7 is 14. The granddaughter is 14, the daughter 28 and the grandmother 56.
A man looks at a portrait and says: "I have no brothers and no sisters, and the father of the man in this portrait is my father's son." Who is in the portrait? Answer: His son. He has no brothers, so "my father's son" can only be himself. The man in the portrait has him for a father: it is his son.
Each of Mrs. Vega's four sons has two sisters. How many children does Mrs. Vega have? Answer: Six. The four boys share the same two sisters. Four sons and two daughters make six children, not twelve.
The four Reed children are Ann, Bob, Cal and Dot, and no two were born in the same year. Ann has two older brothers. Dot is the youngest. Bob is older than Cal. Who is the oldest, and who is second youngest? Answer: Bob is the oldest and Ann is second youngest. Ann's two older brothers can only be Bob and Cal, so both come before her, and Dot comes last. Bob is older than Cal. From the oldest: Bob, Cal, Ann, Dot.
Grandma Bea has three children and nine grandchildren. Each of her children has at least two children, and no two of them have the same number. How many children are in the largest of the three families? Answer: Four. Three different numbers, each two or more, must add up to nine. The smallest such set is 2, 3 and 4, and that already makes nine, so it is the only one. The largest family has four children.
Grandma Rosa has two daughters and no other children. Each daughter has two sons and no other children. How many first cousins does each of the grandsons have? Answer: Two. Each boy has one brother, who is not a cousin. His cousins are the two sons of his mother's sister. Four grandsons, but two cousins each.
In the Ito family every child has at least one brother and at least one sister. What is the smallest number of children the family can have? Answer: Four. A boy needs a brother, so there are at least two boys. A girl needs a sister, so there are at least two girls. Both boys and girls must be there, or somebody would lack a brother or a sister. Two and two make four.
Kai's father marries Lani's mother. Kai and Lani were both born before the wedding, and they share no parent. What are Kai and Lani to each other? Answer: Stepbrother and stepsister. They have no parent in common, so they are not brother and sister by birth. Each is the child of the other's stepparent, and that is what a stepbrother or stepsister is.
Mrs. Hale holds up a photo of a man and says: "This man's mother is my mother's only daughter." What is the man to Mrs. Hale? Answer: Her son. Her mother's only daughter is Mrs. Hale herself. So the man's mother is Mrs. Hale, and he is her son.
Nia's brother has a daughter, Zoe. Zoe's mother has a mother-in-law. What is that mother-in-law to Nia? Answer: Her mother. Zoe's mother is the wife of Nia's brother. Her mother-in-law is her husband's mother, and the mother of Nia's brother is Nia's mother too.
Nora has three times as many sisters as brothers. Her brother Sam has seven times as many sisters as brothers. How many children are in the family? Answer: Nine. Try the number of boys. With one boy, Sam would have no brothers at all. With two boys, Nora has two brothers and so six sisters, which makes seven girls, and Sam has seven sisters and one brother. That fits: seven girls and two boys, nine children. With three boys or more the two clues no longer agree.
The Novak family has six children. Every boy has more sisters than brothers, and every girl has more brothers than sisters. How many of the six are boys? Answer: Three. With four boys or more, a boy would have at least three brothers and at most two sisters. With four girls or more, a girl would have at least three sisters and at most two brothers. Three and three works: each boy has two brothers and three sisters, and each girl the other way round.
The Parks have six children. Each daughter has exactly two sisters. How many sons do the Parks have? Answer: Three. A girl with two sisters is one of three girls. Six children less three daughters leaves three sons.
Paul and Quinn are brothers. Paul has a son, Ray, and Ray has a daughter, Sia. What is Quinn to Sia? Answer: Her great-uncle. Paul is Sia's grandfather, her father's father. The brother of a grandfather is a great-uncle.
Ray is an only child, and so is his father. Ray's mother has one sister and no brothers, and that sister has no children. Counting only people related to him by birth, how many aunts, uncles and first cousins does Ray have? Answer: One aunt, no uncles and no cousins. His father has no brothers or sisters, so nothing comes from that side. His mother's one sister is his aunt. She has no children, and a first cousin is the child of an aunt or an uncle, so Ray has none.
Ruth has as many brothers as sisters. Her brother Abel has twice as many sisters as brothers. How many children are in the family? Answer: Seven. Ruth does not count herself, so there is one more girl than boys. Abel does not count himself either. Four girls and three boys fit: Ruth has three sisters and three brothers, and Abel has four sisters and two brothers. That is seven children.
Sara has a brother, Tim. Tim is married. What is the father-in-law of Tim's wife to Sara? Answer: Her father. A wife's father-in-law is her husband's father. Tim's father is also Sara's father, since they are brother and sister.
Tom has three more sisters than brothers. His sister Sue has twice as many sisters as brothers. How many children are in the family? Answer: Four. Suppose Tom has no brothers: then he has three sisters, and the family is one boy and three girls. Check Sue: she has two sisters and one brother, twice as many. With more boys the two clues stop agreeing, so there are four children.
Walt is Viv's father-in-law. Viv's husband has a sister, Xena, and Xena has a daughter, Yara. What is Walt to Yara? Answer: Her grandfather. A father-in-law is the husband's father, so Walt is the father of Viv's husband. Xena is that man's sister, so Walt is Xena's father too. Yara is Xena's daughter, which makes Walt her grandfather.
Your aunt is the sister of one of your parents. She has exactly one brother, and he is not your uncle. What is he to you? Answer: Your father. If she were your mother's sister, her brother would be your mother's brother, your uncle. So she is your father's sister, and her only brother is your father.

Weighing, pouring and crossing 20

A camper has a 6-cup bottle, a 4-cup bottle and a stream to fill them from, with no marks on either bottle. Can she end up with exactly 3 cups in one bottle? Say why or why not. Answer: No. Every amount she can make is even. Filling gives 6 or 4, emptying gives 0, and pouring only adds or takes away even amounts from even amounts. Three is odd, so it can never appear.
A cook has a 7-cup pot, a 4-cup pot and a faucet, and needs exactly 5 cups of water. Filling a pot, emptying a pot and pouring one pot into the other each count as one move. What is the fewest moves that leave exactly 5 cups in a pot? Answer: Eight moves. Fill the 4-cup pot. Pour the 4-cup pot into the 7-cup pot. Fill the 4-cup pot. Pour the 4-cup pot into the 7-cup pot until the 7-cup pot is full. Empty the 7-cup pot. Pour the 4-cup pot into the 7-cup pot. Fill the 4-cup pot. Pour the 4-cup pot into the 7-cup pot. The 7-cup pot now holds 5 cups.
A farmer must row a cat, a mouse and a wheel of cheese across a river. The boat holds the farmer and one of the three. Left alone together, the cat would chase the mouse, and the mouse would nibble the cheese. What must the farmer carry on the first trip, and how many one-way trips does the whole job take? Answer: The mouse first, and seven trips in all. Only the cat and the cheese can be left together, so the mouse goes first (1). Row back empty (2). Take the cat over (3) and bring the mouse back (4). Take the cheese over (5), row back empty (6), and fetch the mouse (7). Starting with the cheese in place of the cat at trip 3 works the same way.
A gardener has an 8-quart can, a 5-quart can and a rain barrel to fill them from. She wants exactly 2 quarts. Filling a can, emptying a can and pouring one can into the other each count as one move. What is the fewest moves that leave exactly 2 quarts in a can? Answer: Four moves. Fill the 5-quart can. Pour the 5-quart can into the 8-quart can. Fill the 5-quart can. Pour the 5-quart can into the 8-quart can until the 8-quart can is full. Two quarts are left in the 5-quart can.
A market stall has a two-pan balance and three weights: 1 pound, 3 pounds and 9 pounds. A customer wants exactly 7 pounds of rice. Weights may go on either pan. Where does each weight go? Answer: The 3-pound weight beside the rice, and the 9-pound and 1-pound weights on the other pan. With the rice and the 3-pound weight on one pan and 9 + 1 = 10 pounds on the other, the pans are level only when the rice weighs 10 - 3 = 7 pounds. No other placing of the three weights leaves 7.
A melon is on one pan of a balance. On the other pan sit half of a melon just like it and a 3-pound weight, and the pans are level. How much does the whole melon weigh? Answer: 6 pounds. Take half a melon off each side in your mind. Half a melon is left on one pan and the 3-pound weight on the other, so half a melon weighs 3 pounds and a whole one weighs 6.
An 8-quart pail is full of milk. Beside it stand an empty 5-quart pail and an empty 3-quart pail. Two neighbors want 4 quarts each, and there are no marks and no faucet: the milk can only be poured from pail to pail. What is the fewest pours that leave 4 quarts in the big pail and 4 quarts in the 5-quart pail? Answer: Seven pours. Pour the 8-quart pail into the 5-quart pail until the 5-quart pail is full. Pour the 5-quart pail into the 3-quart pail until the 3-quart pail is full. Pour the 3-quart pail into the 8-quart pail. Pour the 5-quart pail into the 3-quart pail. Pour the 8-quart pail into the 5-quart pail until the 5-quart pail is full. Pour the 5-quart pail into the 3-quart pail until the 3-quart pail is full. Pour the 3-quart pail into the 8-quart pail. The 8-quart pail and the 5-quart pail now hold 4 quarts each.
At a lemonade stand there are a 9-cup pitcher, a 4-cup pitcher and a faucet. An order needs exactly 6 cups. Filling a pitcher, emptying a pitcher and pouring one pitcher into the other each count as one move. What is the fewest moves that leave exactly 6 cups in a pitcher? Answer: Eight moves. Fill the 9-cup pitcher. Pour the 9-cup pitcher into the 4-cup pitcher until the 4-cup pitcher is full. Empty the 4-cup pitcher. Pour the 9-cup pitcher into the 4-cup pitcher until the 4-cup pitcher is full. Empty the 4-cup pitcher. Pour the 9-cup pitcher into the 4-cup pitcher. Fill the 9-cup pitcher. Pour the 9-cup pitcher into the 4-cup pitcher until the 4-cup pitcher is full. The 9-cup pitcher now holds 6 cups.
Five campers stand on one bank of a river with a canoe that holds two. The canoe cannot cross empty: somebody has to paddle it back each time. What is the fewest one-way trips that put all five on the far bank? Answer: Seven trips. Each trip over carries two, and each trip back returns one, so a round trip gains one camper on the far side. Three round trips move three campers in six trips, and a last trip over takes the remaining two. That is seven trips.
Five jars hold marbles. In four jars every marble weighs 10 grams; in one jar every marble weighs 11 grams. You may read a kitchen scale once. How do you find the jar of heavy marbles? Answer: Take one marble from the first jar, two from the second, three, four and five from the others, and weigh all fifteen together. Fifteen 10-gram marbles would weigh 150 grams. Each heavy marble adds 1 gram, so the number of extra grams is the number of marbles you took from the heavy jar, and that tells you which jar it is: 151 means the first, 155 the fifth.
Four bars of soap look the same, but one was cut a little small and is lighter. With a two-pan balance and no weights, what is the fewest weighings that always find the light bar? Answer: Two weighings. One weighing has only three outcomes (left down, right down, level), which cannot tell four bars apart. Two are enough: weigh one bar against one. If a pan rises, that bar is the light one. If they balance, weigh the other two against each other.
Four hikers reach a rope bridge at night with one lantern. The bridge holds two at a time, nobody crosses without the lantern, and a pair walks at the slower hiker's pace. Alone they would take 1, 2, 6 and 9 minutes. What is the shortest time in which all four can be across? Answer: 16 minutes. Send the two fastest first (2 minutes). The 1-minute hiker brings the lantern back (1). The two slowest cross together (9). The 2-minute hiker brings the lantern back (2). The two fastest cross again (2). That is 2 + 1 + 9 + 2 + 2 = 16. Letting the fastest hiker walk each of the others over takes 2 + 1 + 6 + 1 + 9 = 19.
Nine marbles look alike, and one is slightly heavier than the other eight. With a two-pan balance and no weights, what is the fewest weighings that are sure to find it? Answer: Two weighings. Weigh three against three. The heavy marble is in the pan that drops, or in the three left out if the pans stay level. From those three, weigh one against one: the pan that drops holds it, and if they balance it is the third.
On a balance, two pears weigh the same as one mango. One mango and one pear together weigh the same as six plums. How many plums weigh the same as one pear? Answer: Two plums. Swap the mango for the two pears it equals: three pears balance six plums. So one pear balances two plums.
Three friends must cross a narrow footbridge in the dark with one flashlight. Two can cross at a time, the flashlight has to go with every crossing, and a pair walks at the slower one's pace. Alone they take 1, 3 and 5 minutes. What is the shortest time to get all three across? Answer: 9 minutes. The 1-minute and the 3-minute friend cross (3 minutes). The 1-minute friend walks the flashlight back (1). Then the 1-minute and the 5-minute friend cross (5). 3 + 1 + 5 = 9.
Three gold-colored coins look the same, but one is a little heavier. You have a balance with two pans and no weights. What is the fewest weighings that are sure to find the heavy coin? Answer: One weighing. Put one coin in each pan and leave the third on the table. If a pan drops, that coin is the heavy one. If the pans stay level, it is the coin on the table.
Three wooden cubes and one ball balance ten marbles. One cube balances one ball and two marbles. All cubes weigh the same, and so do all marbles. How many marbles balance the ball? Answer: One marble. Trade each cube for a ball and two marbles. The first pan then holds four balls and six marbles against ten marbles. Take six marbles off both pans: four balls balance four marbles, so a ball weighs the same as one marble.
Two parents and their two children must cross a lake in a rowboat that carries either one adult or up to two children, never an adult and a child together. Everyone can row. What is the fewest one-way trips that take the whole family across? Answer: Nine trips. Both children row over (1) and one rows back (2). A parent rows over (3) and the other child rows back (4). That is four trips to move one parent, with both children back at the start. Repeat for the second parent (trips 5 to 8). Then both children row over together (9).
You have a 5-cup jar, a 3-cup jar and a faucet, and no marks on the glass. You need exactly 1 cup. Filling a jar, emptying a jar and pouring one jar into the other each count as one move. What is the fewest moves that leave exactly 1 cup in a jar? Answer: Four moves. Fill the 3-cup jar. Pour the 3-cup jar into the 5-cup jar. Fill the 3-cup jar. Pour the 3-cup jar into the 5-cup jar until the 5-cup jar is full. One cup is left in the 3-cup jar.
You have a 5-minute sand timer and a 3-minute sand timer, and no clock. How can you time exactly 7 minutes from the moment you start? Answer: Start both; flip the small timer when it runs out, and flip it again the moment the big timer runs out. Start both timers. At 3 minutes the small one is empty: turn it over. At 5 minutes the big one is empty, and the small one has been running for 2 minutes, so 2 minutes of sand lie in its lower half. Turn the small one over right then, and those 2 minutes run back: 5 + 2 = 7.

What comes next and odd one out 20

Four of these numbers are built the same way. Which is the odd one out? 123, 345, 567, 689, 789. Answer: 689. In the other four the digits climb one at a time: 1-2-3, 3-4-5, 5-6-7, 7-8-9. In 689 the first step is a jump of two.
Four of these numbers pair up. Which is the odd one out? 13, 17, 19, 31, 71. Answer: 19. 13 and 31 are each other read backward, and so are 17 and 71. Read 19 backward and you get 91, which is not in the list.
Four of these numbers share something. Which is the odd one out? 11, 13, 15, 17, 19. Answer: 15. 15 is 3 x 5. The other four can be divided only by 1 and by themselves.
Four of these numbers share something. Which is the odd one out? 18, 27, 45, 64, 81. Answer: 64. The digits of the other four add up to 9, and each is in the 9 times table. 6 + 4 is 10, and 64 is not.
Four of these numbers share something. Which is the odd one out? 8, 27, 64, 100, 125. Answer: 100. 8 is 2 x 2 x 2, 27 is 3 x 3 x 3, 64 is 4 x 4 x 4 and 125 is 5 x 5 x 5. No whole number multiplied by itself three times makes 100.
What letter comes next? A, C, F, J, O, and then? Answer: U. The jumps grow by one letter each time: 2 from A to C, then 3, 4 and 5. A jump of 6 from O lands on U.
What letter comes next? Z, X, V, T, and then? Answer: R. The letters run backward through the alphabet, skipping one each time: after T, skip S and land on R.
What number comes next? 1, 1, 2, 3, 5, 8, and then? Answer: 13. From the third number on, each one is the sum of the two before it: 5 + 8 = 13.
What number comes next? 1, 11, 21, 1211, 111221, and then? Answer: 312211. Each number reads the one before it aloud. 1 is "one 1", so 11. 11 is "two 1s", so 21. 21 is "one 2, one 1", so 1211. 111221 is "three 1s, two 2s, one 1": 312211.
What number comes next? 1, 2, 2, 4, 8, 32, and then? Answer: 256. From the third number on, each one is the two before it multiplied: 1 x 2 = 2, 2 x 2 = 4, 2 x 4 = 8, 4 x 8 = 32, and 8 x 32 = 256.
What number comes next? 1, 2, 6, 24, 120, and then? Answer: 720. Multiply by 2, then by 3, then by 4, then by 5. The next step multiplies by 6: 120 x 6 = 720.
What number comes next? 1, 3, 7, 15, 31, and then? Answer: 63. Each number is double the one before, plus 1: 31 + 31 + 1 = 63.
What number comes next? 1, 4, 3, 6, 5, 8, and then? Answer: 7. Two steps take turns: add 3, then take away 1. After 5 + 3 = 8 comes 8 - 1 = 7.
What number comes next? 2, 3, 5, 7, 11, 13, and then? Answer: 17. These are the numbers that can be divided only by 1 and by themselves, in order. After 13, the next is 17: 14, 15 and 16 can all be divided by something smaller.
What number comes next? 2, 5, 8, 11, and then? Answer: 14. Each number is 3 more than the one before: 11 + 3 = 14.
What number comes next? 2, 6, 12, 20, 30, and then? Answer: 42. The gaps are 4, 6, 8, 10, growing by 2 each time. The next gap is 12, and 30 + 12 = 42. Each number is also two neighbors multiplied: 1 x 2, 2 x 3, up to 6 x 7.
What number comes next? 2, 6, 18, 54, and then? Answer: 162. Each number is 3 times the one before: 54 x 3 = 162.
Which is the odd one out? An inch, a foot, a yard, a mile, a pound. Answer: Pound. An inch, a foot, a yard and a mile measure length. A pound measures weight.
Which month is the odd one out? January, March, June, July, August. Answer: June. June has 30 days. The other four have 31.
Which shape is the odd one out? A square, a triangle, a circle, a rectangle, a pentagon. Answer: Circle. A circle has no straight sides and no corners. The other four are made of straight sides: 4, 3, 4 and 5 of them.

How this list was compiled

Written by the Game Night Generator editors on October 3, 2026: 100 deduction puzzles in five sets of 20, each with one answer that follows from the clues and with the reasoning printed under the answer. Every puzzle was checked by computer on the day it was written, by trying every case: each who-did-it against every suspect, each seating or ownership puzzle against every arrangement, each family puzzle against a drawn family tree or every family size up to 40 children, each pouring and crossing puzzle against every sequence of moves, and each number, letter or shape pattern against its rule. A puzzle that allowed two answers was rewritten. Several forms are traditional and belong to nobody (the heavy coin on a balance, two jugs and a faucet, the river crossing, the bridge at night, the look-and-say numbers); each is told here with the editors' own numbers, names and wording, and none was copied from a puzzle book or a site. The three levels are the editors' judgment; nobody timed the puzzles with a group. Licence: own work