Logic riddles are those whose answers can be deduced with only logic. These tricky riddles are often harder than the others.
Question: There is a prison with 100 prisoners, each in separate cells with no form of contact. There is an area in the prison with a single light bulb in it. Each day, the warden picks one of the prisoners at random, even if they have been picked before, and takes them out to the lobby. The prisoner will have the choice to flip the switch if they want. The light bulb starts off.
When a prisoner is taken into the area with the light bulb, he can also say "Every prisoner has been brought to the light bulb." If this is true all prisoners will go free. However, if a prisoner chooses to say this and it's wrong, all the prisoners will be executed. So a prisoner should only say this if he knows it is true for sure.
Before the first day of this process begins, all the prisoners are allowed to get together to discuss a strategy to eventually save themselves.
What strategy could they use to ensure they will go free?
Answer: Only allow one prisoner to turn the light bulb off and all of the others turn it on if they have never turned it on before. If they have turned it on before they do nothing. The prisoner that can turn it off then knows they have all been there and saves them all when he has turned it off 99 times.
By Albert Einstein
Question: There are 5 houses painted 5 different colors. In each house lives a person with a different nationality. These 5 people each drink a certain type of beverage, smoke a certain brand of cigar, and keep a certain pet. None of them have the same pet, smoke the same brand of cigar, or drink the same beverage.
The Brit lives in the red house.
The Swede keeps dogs as pets.
The Dane drinks tea.
The green house is on the left of the white house.
The green homeowner drinks coffee.
The person who smokes Pall Mall rears birds.
The owner of the yellow house smokes Dunhill.
The man living in the center house drinks milk.
The Norwegian lives in the first house.
The man who smokes Blend lives next to the one who keeps cats.
The man who keeps the horse lives next to the man who smokes Dunhill.
The owner who smokes Bluemaster drinks beer.
The German smokes prince.
The Norwegian lives next to the blue house.
The man who smokes Blend has a neighbor who drinks water.
Who owns the fish?
Answer: The German. It's easiest to solve this riddle by creating a grid organized by order of the houses, you can then fill in the house number of the Norwegian, the person who drinks milk, and the blue house:
These facts can all also be determined from the clues:
Brit - Red House
Swede - Dogs
Dane - Tea
Green House - Coffee
Pall Mall - Birds
Yellow House - Dunhill
Blue-masters - Beer
German - Prince
Green House is to left of the White House
Blends is next to Cats
Horse is next to Dunhill
Blends is next to Water
With this information these facts can be determined:
This info leads to a single color order:
The following information can now be determined:
With this version of the table we can now find the information pertaining to solving the riddle completely:
Question: There is a basket full of hats. 3 of them are white and 2 of them are black. There are 3 men Tom, Tim, and Jim. They each take a hat out of the basket and put it on their heads without seeing the hat they selected or the hats the other men selected. The men arrange themselves so Tom can see Tim and Jim's hats, Tim can see Jim's hat, and Jim can't see anyone's hat.
Tom is asked what color his hat is and he says he doesn't know.
Tim is asked the same question, and he also doesn't know.
Finally, Jim is asked the question, and he does know.
What color is his hat?
Answer: The hat is white. If Tom doesn't know his hat color then the other two men's hats cannot be both black otherwise he would know his is white. When Tim doesn't know his hat color either, that means Jim's hat could not be black otherwise Tim would have to know his hat was white to fulfill the information discovered through Tom's answer.
Question: If you have an 11 minute and 13 minute hourglass, how can you accurately time 15 minutes?
Answer: Start both hourglasses then when the 11 minute hourglass has finished immediately flip it again. When the 13 minute hourglass runs out the 11 minute hourglass will have 9 minutes left, so flip it and it will last another 2 minutes, 13 minutes + 2 minutes = 15 minutes.
Question: You have a glass of water that looks about half full. How can you tell, only using the glass of water itself, if the glass is half full or not?
The glass is a right cylinder.
Answer: Tip the glass of water until the water reaches the rim of the glass and if the water lines up perfectly with the bottom rim of the glass, it is half full.
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