Riddles I found and liked. They mostly have satisfying answers.
Riddle: You have 11 coins. One of them is fake, and has a different weight from the others: it can be either lighter or heavier.
Riddle: You are at the top of a 100 m cliff with a 75 m rope and a knife. A branch sticks out 50 m below. How do you get down safely?
Riddle: You are looking to your reflection in a mirror. If you move your right hand, your reflection seems to be moving its left hand. However, if you move…
Riddle: Three scoundrels must split $100 by majority vote, each wanting the most money. What is the outcome? A game theory riddle I have not solved yet.
Riddle: A suitcase holds a million dollars only if a 95% accurate machine predicted you would drink the poison. Do you drink it? A version of Newcomb’s paradox.
Riddle: You are blind, with two blue pills and two red pills. You must take exactly one of each today and tomorrow. How do you do it?
Riddle: Can you find a 4 digits number that gets reversed when multiplied by 4?
Riddle: Cut a rope at two random places. What is the probability that the three pieces can form a triangle?
Riddle: A farmer has 100kg of potatoes. At the start, they are composed of 99% of water (the water is 99% of the total weight) and 1% of dry matter (the dry…
Riddle: Albert and Bernard just become friends with Cheryl, and they want to know when her birthday is. Cheryl gives them a list of 10 possible dates.
Riddle: How do you make 26 by using 5, 5, 5 and 1. You have to use each exactly once. You can use the basic math operations (+, -, *, /, (, ) ).
Riddle: Four hidden coins on a spinning quadrant, five turns, and a light that turns on only when all four match. Find a strategy that always works.
Riddle: In a far away land, it was known that if you drank poison, the only way to save yourself is to drink a stronger poison in the next 12 hours, which…
Riddle: The warden meets with 23 new prisoners when they arrive. He tells them, “You may meet today and plan a strategy. But after today, you will be in…
Riddle: A mother is 21 years older than her child. In 6 years she will be 5 times older. Where is the father? A maths riddle with a strange answer.
Riddle: There is a stack of 100 coins. Each coin has a silver side and a golden side. 20 coins are silver side up. The rest is golden side up. You are in a…
Riddle: If 3 cats take 3 minutes to catch 3 mouses, how many cats are needed to catch 100 mouses in 100 minutes ?
Riddle: If I can make it around a running track once by going 10 km/h, what speed should I be running a second lap to have an average speed of 20 km/h for the…
Riddle: Imagine a 747 is sitting on a conveyor belt, as wide and long as a runway. The conveyor belt is designed to [try to ?] exactly match the speed of the…
Riddle: The evil professor says to the students: you are going to have an exam next week. I’m not telling you which day, but I am telling you that it will be…
Riddle: You are in a square forest of side 100km. You are 2km away from its border, but you don’t know in what direction or at what angle (It could be at 2km…
Riddle: Jack is looking at Anne, but Anne is looking at George. Jack is married, but George is not. Is a married person looking at an unmarried person?
Riddle: A lady has two children. One is a boy. What are the chances of the other child also being a boy?
Riddle: Alice sees 12 trees, Bob sees 8, and neither knows the other’s count. Each day they are asked if there are 18 or 20 trees. A common knowledge puzzle.
Riddle: A group of perfect logicians with assorted eye colors live on an island. A visitor makes one remark. Who leaves the island, and when?
Riddle: Four shapes, one is the odd one out. Find the exception and explain why.
Riddle: Alice looks at five cards, hands four to Bob, and Bob names the fifth. No code, no sleight of hand. How does the trick work?
Riddle: You have a lighter and two lengths of rope that burn for exactly 1 hour each. They do not burn consistently so you cannot, for example, cut one in half…
