Logic Riddles With Answers
Updated · Best Riddles With Answers editorial team
Quick answer: Logic riddles give you a handful of clues and one answer that must follow from them. This page has 42 of them with answers, and every solution states its reasoning so you can check it. Start with simple ordering and syllogisms, then move on to truth tellers, liars, grids and code breaking.
Easy Logic Riddles
All roses are flowers, and some flowers fade quickly. Can you be sure that some roses fade quickly?
No. The flowers that fade quickly might all be other kinds, so the clues do not settle it.
Tom is taller than Sam, and Sam is taller than Raj. Who is the shortest?
Raj, because Tom > Sam > Raj.
Three houses stand in a row: red, blue and green. The red house is left of the blue one, and the green house is at the right end. Which house is in the middle?
Blue. The order must be red, blue, green.
All cats have tails, and Tom has no tail. Is Tom a cat?
No. If Tom were a cat he would have a tail.
Anna is older than Ben, Ben is older than Cy, and Dee is younger than Cy. Who is the second oldest?
Ben, because the order is Anna, Ben, Cy, Dee.
Today is Wednesday. What day of the week was it 100 days ago?
Monday. 100 is 14 weeks plus 2 days, and two days before Wednesday is Monday.
Mia is Ben's sister, and Ben is Cora's father. How is Mia related to Cora?
She is Cora's aunt, being the sister of Cora's father.
Which number is the odd one out: 2, 4, 6, 9, 10?
9, the only odd number.
If it rains, the ground gets wet. The ground is wet. Must it have rained?
No. Someone could have watered it, or a pipe could have burst.
Ana, Beth and Cora each take a different fruit from apple, banana and cherry. Ana takes neither banana nor cherry, and Beth does not take banana. Who takes the cherry?
Beth. Ana takes the apple, and Beth cannot have the banana.
If all bloops are razzies and all razzies are lazzies, are all bloops lazzies?
Yes, because each bloop is a razzie and each razzie is a lazzie.
What number comes next: 1, 1, 2, 3, 5, 8?
13. Each number is the sum of the two before it, and 5 + 8 = 13.
Trickier Logic Riddles
Two guards stand at two doors. One door leads to freedom and one to danger. One guard always tells the truth and one always lies, and you do not know which is which. What single question to either guard finds the safe door?
Ask, 'Which door would the other guard say is safe?' Then take the opposite door. A liar misreports the truth teller, and the truth teller reports the liar's lie.
Three switches outside a closed room control three bulbs inside. You can enter the room only once. How do you match each switch to its bulb?
Turn on switch 1 for a few minutes, then turn it off and turn on switch 2. Enter: the lit bulb is switch 2, the warm unlit bulb is switch 1, and the cold one is switch 3.
Ann says, 'Ben is lying.' Ben says, 'Cal is lying.' Cal says, 'Ann and Ben are both lying.' Who is telling the truth?
Only Ben. If Cal were honest, Ann and Ben would both lie, but Ann lying means Ben is honest. So Cal lies, which makes Ben's claim true, and Ann's claim false.
Three doors have signs. Door 1: 'The treasure is here.' Door 2: 'The treasure is not here.' Door 3: 'The treasure is not behind door 1.' Exactly one sign is true. Where is the treasure?
Behind door 2. Then only the sign on door 3 is true. Door 1 gives two true signs, and door 3 gives two.
Ann finished ahead of Ben. Cal finished behind Ben but ahead of Dee. Eve finished ahead of Ann. Who came third?
Ben. The order is Eve, Ann, Ben, Cal, Dee.
Sam is twice as old as Jo was when Sam was as old as Jo is now. Sam is 24. How old is Jo?
18. Six years ago Sam was 18 and Jo was 12, and Sam is now 24, which is twice 12.
If it is a dog, it is a mammal. This animal is not a mammal. What can you say about it?
It is not a dog.
If the day after tomorrow is Thursday, what day was yesterday?
Monday. Today is Tuesday, so yesterday was Monday.
Alice has 3 more apples than Ben, and Ben has twice as many as Cara. Together they have 28. How many does each have?
Cara has 5, Ben has 10 and Alice has 13. With Cara = x, 5x + 3 = 28 gives x = 5.
A small town has two barbers. One has a messy haircut and the other has a perfect haircut. Which one should you choose?
The one with the messy haircut. There are only two barbers, so each cuts the other's hair, and the perfect cut was done by the messy one.
Pam is Quinn's sister, Quinn is Ray's mother, and Ray is Sue's father. How is Pam related to Sue?
She is Sue's great-aunt, being the sister of Sue's grandmother.
Alice is taller than Ben, Cara is shorter than Ben, and Dan is taller than Alice. Who is the second tallest?
Alice, because the order is Dan, Alice, Ben, Cara.
Hard Logic Riddles
A lock has a 3 digit code. 682: one digit is right and in the right place. 614: one digit is right but in the wrong place. 206: two digits are right but both in the wrong place. 738: nothing is right. 780: one digit is right but in the wrong place. What is the code?
042. The 738 clue removes 7, 3 and 8, and the others then force the digits 0, 4 and 2 into the only places that fit all five clues.
On an island, knights always tell the truth and knaves always lie. A says, 'B is a knave.' B says, 'A and I are the same type.' What are A and B?
A is a knight and B is a knave. If A were a knave, B would be a knight, but then B's claim would be false.
Ava, Ben and Cy live in houses 1, 2 and 3 in a row and own a cat, a dog and a bird. Ben is in house 1 and is allergic to feathers. The dog is in house 3. Ava does not own the cat. Cy lives next to the bird's owner. Who owns what?
Ben has the cat, Ava has the bird and Cy has the dog. The bird must be in house 2, so Ava owns it, and Cy lives next door in house 3.
Five people sit in seats 1 to 5. Eve is in seat 3. Finn is not next to Eve. Gus is next to Finn. Hana is somewhere left of Gus. Ivy is not in seat 1. Who is in seat 2?
Ivy. Finn must be in seat 5, so Gus is in 4, and Hana and Ivy take seats 1 and 2 with Ivy in 2.
Room 1's sign says: 'In this room there is a lady and in the other room there is a tiger.' Room 2's sign says: 'In one of these rooms there is a lady, and in one of these rooms there is a tiger.' One sign is true and one is false. Which room has the lady?
Room 2. If the first sign were true the second would be true as well. So the first is false, the second is true, and the rooms differ.
You have two eggs and a 100 floor building. An egg breaks if dropped from above a certain floor. What is the fewest drops that always finds that floor?
14. Drop from floors 14, 27, 39 and so on, going up 13, 12, 11 floors each time. 14 + 13 + 12 + ... + 1 = 105, which covers 100 floors.
One of 1,000 bottles of wine is poisoned and the poison shows after a day. How few testers are needed to find the bottle in one day?
10. Number the bottles in binary, one tester per binary digit, and the set of dead testers spells the bottle number, since 2 multiplied by itself 10 times is 1,024.
Ten bags each hold ten coins. One bag holds forged coins that each weigh 1 gram less than a real 10 gram coin. With one weighing on a digital scale, how do you find the bad bag?
Take 1 coin from bag 1, 2 from bag 2 and so on up to 10 from bag 10. The total is short by as many grams as the bad bag's number.
A large cube is painted red on all faces, then cut into 27 equal small cubes. How many small cubes have exactly two red faces?
12. They are the edge pieces, one in the middle of each of the cube's 12 edges.
What number comes next: 1, 2, 4, 7, 11, 16?
22. The gaps are 1, 2, 3, 4, 5, so the next gap is 6.
Quick-Fire Logic Riddles
What day comes next: Monday, Wednesday, Friday?
Sunday.
If A = 1, B = 2 and C = 3, what is the total of the letters in CAB?
Six.
No cats are birds, and Tweety is a bird. Is Tweety a cat?
No.
Which is the odd one out: triangle, square, circle, pentagon?
The circle, which has no straight sides.
Which is the odd one out: Mars, Venus, Moon, Earth?
The Moon, which is not a planet.
What letter comes next: Z, X, V, T?
R.
A is north of B, and B is north of C. Which direction is C from A?
South.
If all squares are rectangles, is every rectangle a square?
No. A rectangle with unequal sides is not a square.
How to Solve Logic Riddles
Write the clues down and treat each one as a rule. For ordering puzzles draw a line of boxes and place names as soon as a clue allows. For truth and lie puzzles, assume one person is honest and follow what that forces; if it contradicts a statement, the opposite must hold. Eliminating options is faster than guessing.
Check the finished answer against every clue, not only the last one. If two answers fit, you have missed a clue or misread one. Notice also what a puzzle does not say: the rose riddle and the rain riddle are classic traps where an answer feels right, yet it does not follow.
Frequently Asked Questions
What is a logic riddle?
A logic riddle gives a set of facts and asks you to work out something that follows from them. No special knowledge is needed, because the answer comes from reasoning alone.
How are logic riddles different from lateral thinking riddles?
A logic riddle has clues that lead to its answer by deduction. A lateral thinking riddle asks you to find a hidden assumption in a story. Both reward careful thought, but logic riddles can be checked step by step.
What is the best way to start solving a logic puzzle?
Look for the most certain clue and place it first. Then use each new fact to rule out options for other clues. A small table or a line of boxes helps keep track of everything.
Where do knights and knaves puzzles come from?
They were popularised by the logician Raymond Smullyan, who used islands with honest knights and lying knaves to teach reasoning. The puzzle on this page is a simple example of the kind.
