Rcambier’s Blog - Riddles!

Three’s a Crowd

From: http://www.twinbear.com/riddles.html

The newcomb poison

You are put into a room with a suitcase and a flask of poison.

The blind pill

You are blind. You have 2 blue pills and 2 red pills in a box.

Reversed number

Can you find a 4 digits number that gets reversed when multiplied by 4?

The rope triangle

You cut a rope in a random place. Then again in another random place.

Potatoes

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 matter is 1% of the…

Surprise birthday

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.

Simple Maths

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 (+, -, *, /, (, ) ).

4 Pieces

There are 4 coins on a quadrant. They are not visible to you.

King’s poison

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 neutralizes the weaker…

Prisoner’s switch

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 isolated cells and will have…

Lost father

Question: A mother is 21 years older than her child. In 6 years the mother will be 5 times older than her baby.

Gold coins

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 totally dark room. How do…

Cats and mouses

If 3 cats take 3 minutes to catch 3 mouses, how many cats are needed to catch 100 mouses in 100 minutes ?

Running in circle

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 two laps ?

Broken plane

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 wheels, moving in the…

Evil professor

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 unexpected (i.e., the…

Lost in the woods

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 with an angle of 16.123…

Peeking

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?

Gender

A lady has two children. One is a boy. What are the chances of the other child also being a boy?

Prisoners and trees

Here is a logic puzzle that depends on the game theory concept of common knowledge.

Blue eyes

A group of people with assorted eye colors live on an island. They are all perfect logicians – if a conclusion can be logically deduced, they will do it instantly. No one…

Exception

Find the exception

Magic logic

At a party last night, my friends Alice and Bob did a magic trick. Any ideas how it worked?

Lighter

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 and burn that. How…