Logical Riddles
The Stanford Enigma
This problem was posed during a reflection test to students at the famous Stanford University.
Find out what the following sentences refer to:
- It's better than God.
- It's worse than the devil.
- The poor have it.
- The rich need it.
- And if we eat it, we die.
The challenge of the emir
A dying emir and feeling life leaving him brings his two sons to him.
He said to them, "You see on the horizon the minaret of the neighboring town?" Well, the one of you whose horse will arrive last at the foot of this minaret will inherit all my immense fortune. then to the stable and go as fast as possible to the foot of the minaret.In view of the words of the emir, why they hurry as well?
A water lily doubles its surface
A water lily doubles its size everyday. Thirty days later, it covers up the whole pond it is on.
How many days did it take for it to cover the quarter of this pond's surface ?
The marriage of the cheating king and the princess
In an old Kingdom, there was a King known to be a great cheater. This King was in love with a young princess who refused each time her advances. One day, tired of all his refusals, he decided to play with her so as not to give him any choice, and to force her to marry him. He brought her into the courtyard of the castle, and took two little stones in hand, discreetly. He then said to him:
"In each of my hands, I have a stone.Choose one of my hands.If you find the white stone, you can leave and I will leave you alone, but if you find the black stone, you will have to marry me. on the field, and if you refuse to choose a hand, you will be executed within the hour! "
The young woman, suspecting that the King had cheated, and that each of his hands contained a black stone, began to think to find a ploy that would allow him to escape. After a little thought, she found the solution ...
How can she escape without marrying the King or being executed?
The dilemma of the farmer
A farmer has to cross a river with a wolf, a goat and a cabbage. For this, he has a boat but he can not leave together:
- The goat and the wolf because it would eat it.
- The cabbage and the goat because it would eat it.
How can he do it?
The bulb and the 3 switches
You are in a room with 3 switches. Only one of these switches can light the bulb in the next room. A door gives access to the next room, but you do not see what's going on inside. You have the right to open the door only once.
How do you know which switch is the right one?
The 2 guards and the 2 doors
Two guards each watch a door. One of these doors leads to Paradise, and the other leads to Hell. We know that one of the guardians is always lying, while the other is only telling the truth. However, we do not know which guard is in front of which door. You want to go to heaven, and you have the right to only one question! Once the door is crossed, it is impossible to go back.
What question will you ask to be sure to find the right door?
The night watchman
A great CEO, Mr. Dupont, has his watchman supervised by a night watchman. He must go on a trip, but the morning of his departure, his night watchman said to him:
- Sir, do not leave. That night, I dreamed that your plane crashed.
Mr. Dupont cancels his trip and learns in the evening, that indeed the plane crashed. To thank his employee, he gives him a large sum of money, but nevertheless, fired him. Why ?