Here is a list of 60 logic prompts, divided into categories to challenge different areas of your reasoning.
🤔 Classic Riddles & Lateral Thinking
These puzzles require you to think "outside the box" and question your initial assumptions. The setup often hides a simple answer in plain sight.
A man is in an elevator. Every day, he goes to the ground floor, gets in, and presses the button for the 10th floor. He gets out on the 7th floor and walks the rest of the way up. On his way down, he takes the elevator from the 10th floor all the way to the ground. Why?
A man pushes his car to a hotel and, upon arriving, knows he is bankrupt. Why?
A man walks into a bar and asks the bartender for a glass of water. The bartender pulls out a gun and points it at him. The man says, "Thank you," and leaves. Why?
A man rides into town on Friday. He stays for three nights and leaves on Friday. How is this possible?
A man is found dead in a field with an unopened package next to him. What happened?
A carrot, a scarf, and five pieces of coal are on a lawn. Nobody put them there. Why are they there?
A woman has two sons who were born on the same hour of the same day of the same year. But they are not twins. How?
You are in a sealed room with three light switches. In an adjacent room, there is a single light bulb (which you cannot see from the switch room). You can flip the switches as much as you want, but you may only enter the bulb's room once. How can you determine which switch controls the bulb?
A man is found dead in a cabin in the woods. He did not die of natural causes. The cabin is locked from the inside, and there are no windows. How did he die?
A woman is found dead in a locked room, hanging from the ceiling, with her feet 3 feet off the ground. The room is completely empty except for a puddle of water directly beneath her. How did she do it?
🐺 River Crossing Puzzles
These are classic constraint-based problems where you must move a group of items across a river, following specific rules.
The Wolf, Goat, and Cabbage: A farmer must transport a wolf, a goat, and a cabbage across a river. His boat can only carry him and one other item. If left alone, the wolf will eat the goat, or the goat will eat the cabbage. How does he do it?
The Jealous Husbands: Three married couples must cross a river in a boat that holds only two people. No woman can be on a bank or in the boat with another man unless her husband is also present.
The Four-Person Bridge: Four people need to cross a rickety bridge at night. They have one flashlight, and the bridge can only hold two people at a time. The flashlight must be carried back and forth. Person A takes 1 minute to cross, B takes 2 minutes, C takes 5 minutes, and D takes 10 minutes. When two cross, they move at the slower person's pace. What is the minimum time for all four to cross?
The Missionaries and Cannibals: Three missionaries and three cannibals must cross a river. The boat holds two people. At no point, on either bank or in the boat, can the cannibals outnumber the missionaries.
⚔️ Knights, Knaves & Liars
In these puzzles, you encounter people who either always tell the truth (Knights) or always lie (Knaves).
The Two Doors: You are in a room with two doors. One leads to freedom, the other to doom. In front of the doors are two guards. One is a Knight, and one is a Knave. You don't know which is which. You can ask one question to one guard to find the door to freedom. What do you ask?
The Fork in the Road: You are at a fork in the road. One path leads to safety, the other to peril. A native of the island is there, but you don't know if they are a Knight or a Knave. What one yes/no question can you ask them to find the path to safety?
The Three Gods: You meet three people: A, B, and C. One is a Knight, one is a Knave, and one is a "Random" (who sometimes lies, sometimes tells the truth). You must ask three yes/no questions to determine which is which. Each question must be directed to only one person. (This is a famously hard puzzle).
The Islander's Statement: You meet an islander who says, "I am a Knave." Is this person a Knight, a Knave, or neither?
A, B, and C: You meet three islanders, A, B, and C.
A says: "B is a Knave."
B says: "A and C are of the same type (both Knights or both Knaves)."
What is C?
The Box Puzzles: There are two boxes, A and B. Each has a sign.
Sign A: "The sign on Box B is true, and the prize is in Box A."
Sign B: "The sign on Box A is false, and the prize is in Box A."
If you know exactly one sign is true, where is the prize?
"I am Normal": You meet three people, A, B, and C. One is a Knight, one is a Knave, and one is a "Normal" (who can lie or tell the truth).
A says: "I am Normal."
B says: "That is true."
C says: "I am not Normal."
What are A, B, and C?
🤯 Paradoxes & Self-Reference
These prompts are statements or scenarios that lead to a contradiction or a logically unresolvable loop.
The Liar Paradox: Is the following sentence true or false: "This statement is false."
The Bootstrap Paradox: A time traveler buys a copy of Hamlet from a modern bookstore, travels back to Elizabethan England, and gives the book to William Shakespeare, who then copies it and publishes it as his own. Who wrote Hamlet?
The Ship of Theseus: A famous ship is kept in a museum. Over the centuries, its wooden planks rot and are replaced one by one until not a single original piece of wood remains. Is it still the same Ship of Theseus?
The Unexpected Hanging: A prisoner is told he will be hanged at noon on one weekday in the following week (Monday-Friday). He will not know the day of the hanging in advance. The prisoner reasons: "It can't be Friday, because if I'm not hanged by Thursday, I'll know it's Friday. If Friday is out, it can't be Thursday (for the same reason)..." He rules out all five days. The executioner hangs him on Wednesday, which is a complete surprise. Where did his logic fail?
The Lottery Paradox: It is reasonable to believe that any single lottery ticket you buy will not win (the odds are, say, 1 in 10 million). However, it is also reasonable to believe that one ticket will win. How can you hold both beliefs: that "ticket #1 won't win," "ticket #2 won't win,"... and "one of the tickets will win"?
The Raven Paradox (Hempel's Paradox): The statement "All ravens are black" is logically equivalent to the statement "All non-black things are non-ravens." If you observe a red apple (which is a non-black thing and a non-raven), does this observation increase your confidence that all ravens are black?
The Barber Paradox: In a village, the barber (a man) shaves all men who do not shave themselves, and only those men. Who shaves the barber?
The Card Paradox: You are given a card. On one side, it says, "The statement on the other side of this card is true." On the other side, it says, "The statement on the other side of this card is false." Can both, one, or neither statement be true?
🏛️ Syllogisms & Deductive Reasoning
These prompts test your ability to draw a valid conclusion from a set of given premises.
Instructions: For prompts 30-36, determine if the conclusion is logically valid or invalid, based only on the premises.
Premise 1: All birds have wings.
Premise 2: Penguins are birds.
Conclusion: Therefore, penguins have wings.
Premise 1: All birds have wings.
Premise 2: Bats have wings.
Conclusion: Therefore, bats are birds.
Premise 1: No A is a B.
Premise 2: All C is a B.
Conclusion: Therefore, no C is an A.
Premise 1: All fish live in water.
Premise 2: Some creatures with gills are fish.
Conclusion: Therefore, all creatures with gills live in water.
Premise 1: Some teachers are funny.
Premise 2: All funny people are nice.
Conclusion: Therefore, some teachers are nice.
Premise 1: If it rains, the ground gets wet.
Premise 2: The ground is wet.
Conclusion: Therefore, it rained. (Is this valid?)
Premise 1: If it rains, the ground gets wet.
Premise 2: It did not rain.
Conclusion: Therefore, the ground is not wet. (Is this valid?)
🧠 Critical Thinking & Scenarios
These prompts are open-ended questions designed to make you analyze concepts, biases, and assumptions.
What is the difference between "truth" and "fact"?
If you replaced every part of your bicycle, one piece at a time, until you had an entirely new set of parts, would it still be the same bicycle?
Is it better to be a dissatisfied genius or a satisfied fool?
How would you explain the color "red" to a person who has been blind since birth?
If a perfect, undetectable counterfeit-money machine existed, would it be wrong to use it if you only printed one dollar? What about a million?
A company's algorithm for hiring is found to be 99% accurate in predicting good employees. However, it is also found to have a bias against a specific minority group. Is it ethical to use this algorithm?
What is the difference between "law" and "justice"? Can a law be unjust?
If you had a machine that could predict the future with 100% accuracy, what is one question you would ask it, and what are the potential consequences of knowing the answer?
Is it more important to be respected or to be liked? Why?
If all jobs were paid the same, regardless of difficulty or skill, what job would you choose and why?
You see a runaway trolley speeding toward five people tied to the tracks. You are standing next to a lever that can divert the trolley onto a different track, where one person is tied up. Do you pull the lever?
(Trolley Problem Variant): You are on a bridge overlooking the track. The only way to stop the trolley from hitting the five people is to drop a heavy weight in its path. The only heavy weight available is a large man standing next to you. Do you push him onto the tracks?
What makes a person "successful"? Define the term.
What is the difference between "knowing" something and "believing" something?
🔢 General Logic & Puzzles
A collection of miscellaneous puzzles that test various forms of logical deduction.
The Wason Selection Task (Classic): You see four cards. Each has a letter on one side and a number on the other. The cards show: [ D ] [ K ] [ 3 ] [ 7 ].
Rule: "If a card has a 'D' on one side, it has a '3' on the other."
Which card(s) must you flip over to prove the rule is true?
The Wason Selection Task (Thematic): You are a bouncer. You see four people. One is drinking beer, one is drinking soda, one is 25, and one is 16.
Rule: "If a person is drinking beer, they must be over 21."
Which person/people do you need to check?
The Zebra Puzzle: Five people live in five different colored houses. They are of different nationalities, drink different beverages, smoke different brands of cigars, and each owns a different pet. You are given a list of 15 clues (e.g., "The Englishman lives in the red house," "The Spaniard owns the dog," "The Ukrainian drinks tea"). The question is: Who drinks water, and who owns the zebra?
The Missing Dollar: Three friends check into a hotel and pay $10 each for a $30 room. Later, the manager realizes the room was only $25. He gives the bellhop $5 to return. The bellhop, not knowing how to split $5 three ways, gives each friend $1 back and keeps $2 for himself.
The Logic: Each friend paid $9 ($10 - $1 refund), for a total of $27. The bellhop kept $2. $27 + $2 = $29. Where did the missing dollar go?
The Nine Balls: You have 9 identical-looking balls. One is slightly heavier than the other 8. Using a balance scale, what is the minimum number of weighings needed to find the heavy ball?
The Twelve Balls: You have 12 identical-looking balls. One is an "odd" ball—it is either slightly heavier or slightly lighter than the others. Using a balance scale, what is the minimum number of weighings needed to find the odd ball and determine if it's heavier or lighter?
Cheryl's Birthday: Albert and Bernard just became friends with Cheryl, and they want to know when her birthday is. Cheryl gives them a list of 10 possible dates:
May 15, May 16, May 19
June 17, June 18
July 14, July 16
August 14, August 15, August 17
Cheryl then tells Albert the month (and only the month) and tells Bernard the day (and only the day).
Albert: "I don't know when her birthday is, but I know that Bernard doesn't know either."
Bernard: "At first I didn't know, but now I know."
Albert: "Then I also know when her birthday is."
When is Cheryl's birthday?
The 100 Prisoners and a Lightbulb: There are 100 prisoners in solitary confinement. There is a central room with one lightbulb (initially off). Every day, the warden randomly selects one prisoner to visit the room. This prisoner can toggle the switch (on-to-off or off-to-on) or do nothing. They can't communicate in any other way. At any time, any prisoner can declare, "All 100 prisoners have visited this room at least once." If they are correct, all are freed. If they are wrong, all are executed. What is their strategy?
The Green-Eyed Dragons: On an island, there are 100 green-eyed dragons. They are perfect logicians. They can see the eye color of every other dragon, but not their own. A rule on the island states that if a dragon ever discovers they have green eyes, they must fly away at midnight. For centuries, they all live in harmony, as none knows their own eye color. One day, a visitor comes and announces to all of them: "At least one of you has green eyes." What happens?
The Two Ropes: You have two ropes, each of which takes exactly 1 hour to burn from one end to the other. They do not burn at a uniform rate (e.g., the first half might take 10 minutes, the second half 50). How can you measure exactly 45 minutes?
No comments:
Post a Comment