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HardestFiltered by tag: logic
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9
4
Three Idols
Here's a classic:
Three gods A, B, and C are called, in some order, True, False, and Random. True always speaks truly, False always speaks falsely, but whether Random speaks truly or falsely is a comp
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Hard
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8
225
Non-Adaptive 12 Identical Balls
Okay - so I posted this puzzle to reddit a few weeks ago and one guy had the following comment:
Same problem, but your solution must be non-adaptive. IOW, specify the weighings that you will make up f
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Hard
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8
8
Prisoners and hats
100 prisoners are standing in a line each 1 seeing the back of the ones in front of him. Each prisoner is given a black or a white hat. If they can guess the color of their hat they can go away freel
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Hard
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13
23
Black and White Hats
There are 100 prisoners in jail. Their guards decide to play a game with them. Here's what happens:
1) The prisoners are lined up in a single file, front to back, such that the prisoner at the back of
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Hard
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1
3
4 buttons and a light bulb
There are two rooms, in one room there is a light bulb, and in the other there is a round table, with 4 buttons arragned in a square on it. Each button may be on or off, and the light bulb will be on o
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Hard
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54
41
All the King's Wine
So there's this king. Someone breaks into his wine cellar where he stores 1000 bottles of wine. This person proceeds to poison one of the 1000 bottles, but gets away too quickly for the king's guard
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Hard
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7
7
The Neighbourhood
People say Einstein suggested that 98% of the world’s population couldn’t figure out the answer to this puzzle. It is not for the faint of heart:
There are 5 houses each with a different color. Th
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Hard
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4
10
Don't Mate in One
This problem was first publicized by Karl Fabel, a German chess problemist.
Find a move for white that will not result in an immediate checkmate of the black king.
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Doable
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5
11
The Stealing Mailman
This is a fairly simple problem that can cause some people trouble.
Kevin and Sophia want to mail high confidential letters between each other. They know that the mailman is crooked and opens the le
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Doable
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19
11
Going to the Track
The London racetrack needs to submit its top three horses to the Kentucky Derby next month in order to compete for a prize. However in a recent electrical storm, all the racetrack's previous race histo
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Doable
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27
45
12 Identical Balls
You have 12 identical balls. One of them is slightly different in weight than the rest. You have three weighs of a balance scale to determine which ball is different and whether it is heavier or li
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Doable
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5
2
Age of Three Kids
One day, a guy from census come into a house. When he rings the bell, a lady comes out. He then asks how many people lives in her house, and their age. And then she says:
I am 45 years old. I have thr
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logic
Submitted by Rifqi Ardia Ramadhan
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Doable
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6
10
Cooking Time
A cook must put a souffle exactly 9 minutes at the oven, but he only have a 7 minutes hourglass and a 4 minutes hourglass.
How can he measure 9 minutes with those clocks?
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Doable
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8
1
Attic Lamp Switch
A downstairs panel contains three on-off switches. One of them controls the lamp in your attic. Using only ONE trip up to the attic, how do you determine which switch controls the lamp?
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Doable
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7
4
Tea and Wine
You take a spoon of wine from a barrel of wine and put it into your cup of tea. Then you return a spoon of the (non-uniform) mixture of tea and wine from your cup and put it in the barrel. Now you ha
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Doable
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