Three men, Mr. White, Mr. Brown and Mr. Green, were in the habit of meeting in a local donut shop every morning for coffee and donuts.
One morning as they were sitting at their usual table, Mr. White remarked, "Hey, will you look at that. We're each wearing a colored baseball cap today." They were: one white cap, one brown cap, and one green cap. But interestingly, no one was wearing a cap of the color that matches his name.
At this, the guy wearing the green cap says, "That doesn't mean anything, it's just coincidence. Shut up and eat your donut."
What color cap is each man wearing?
Spoiler:Mr. White is wearing the brown cap, Mr. Green is wearing the white cap, and Mr. Brown is wearing the green cap. The man wearing the green cap responded to Mr. White, meaning Mr. White could not have been wearing the green cap. He also could not have been wearing the white cap as per the rules of the riddle. By process of elimination, we can deduct that he must have been wearing the brown cap. That leaves Mr. Brown with the green cap and Mr. Green with the white cap.
I am not a square, but my length equates to my width. What am I?
Spoiler:I am a book.
How far can a dog run into a forest?
Spoiler:Half-way; after that, he's running out.
For the sake of this riddle, just imagine that in order to cure yourself of poisoning, you must drink a stronger poison. If you do that, both poisons will be impotent and you'll be safe. I know it makes no sense, but just pretend that it does.
In a faraway land, the king wanted to have the strongest poison in existence, in order never to be assassinated by way of poisoned drink. He summoned his alchemist, who was rumored to have the recipe to the strongest poison, and his cook. He told them that they had one week to concoct their strongest poison.
At the end of that week, they would reconvene and have a contest. Each person would drink the other person's poison, and then their own. If their poison was strongest, they would live, and the king would keep that poison. The cook knew that he would never be able to make a poison stronger than the alchemist's, so he came up with a clever plan.
When they met again before the king, the exchange of poisons took place. The cook lived, and the king didn't get what he wanted in the first place.
What was the cook's plan? How did he win the contest?
Spoiler:He made both a poison and a soup. He drank his poison before the contest, then brought the soup to the contest. He drank the alchemist's poison, which neutralized the one he drank prior to the contest. Then he drank the delicious soup. The alchemist, on the other hand, drank the delicious soup followed by his poison. The alchemist died by his own poison and the king was left with a recipe for soup.
A spy wants to enter a secret meeting in order to acquire top secret information. When he approaches the building where the meeting is being held, he finds that there is a guard standing out front. The spy decides to hide in some nearby bushes and find out how the members get inside.
A man walks up, and the guard says, "Twelve."
The man replies, "Six."
The guard lets him in.
A second man walks up, and the guard says, "Six."
The man replies, "Three."
The guard lets him in.
Thinking he had seen enough, the spy walks up to the guard. The guard says, "Ten."
The spy says, "Five."
He was rejected.
Why was he wrong? What should he have said instead?
Spoiler:He should have said, "Three." There are six letters in the word "twelve," three letters in the word "six," and three letters in the word, "ten."
You are walking home and come to a fork in the road. One of the paths leads home and the other one leads to certain doom. You don't know which is which. Fortunately, there's a man who built his house at the fork. You know that he either always lies or always tells the truth, but you don't know which. You need to ask him which way to go, but from only one question must be able to tell which way is home. What do you ask him?
Spoiler:Ask him, "If your stance about honesty were reversed, which way would you tell me to go?" The liar would be speaking from the stance of the truth-teller, so he is supposed to give you the right path, but he lies, so he'd give you the wrong path. The truth-teller, speaking from the point of the liar, would give you the wrong path as well. Then you just follow the path you weren't told to and you're home safe.
There are four fruits in four sealed boxes. One hundred forty-eight people were asked to guess which fruits were in which boxes. At the end of the test, 36 people didn't guess any of the fruits correctly. Thirty-eight guessed one fruit correctly, and thirty-nine guessed two of them correctly. Using your powers of deduction, can you determine how many people correctly guessed exactly three fruits correctly?
Spoiler:The answer is zero. If you correctly guess exactly three out of the four fruits correctly, then it is impossible not to be able to guess the fourth fruit correctly.
Isaac and Albert were excitedly describing the result of the Third Annual International Science Fair Extravaganza in Sweden. There were three contestants, Louis, Rene, and Johannes. Isaac reported that Louis won the fair, while Rene came in second. Albert, on the other hand, reported that Johannes won the fair, while Louis came in second.
In fact, neither Isaac nor Albert had given a correct report of the results of the science fair. Each of them had given one correct statement and one false statement. What was the actual placing of the three contestants?
Spoiler:Johannes came in first place, Rene came in second place, and Louis came in third place. If Isaac was correct about Louis winning the fair, then both of Albert's statements would have been false. However, If Louis had come in second like Albert had said, then both of Isaac's statements would have been false. Therefore, the only two statements that could co-exist are that Johannes came in first place and Rene came in second place, meaning Louis must have come in third place.
Your sock drawer contains ten pairs of white socks and ten pairs of black socks. If you're only allowed to take one sock from the drawer at a time and you can't see what color sock you're taking until you've taken it, how many socks do you have to take before you're guaranteed to have at least one matching pair?
Spoiler:Three socks; if you take three then you're guaranteed at least two of one color.
A mountain goat attempts to scale a cliff sixty feet high. Every minute, the goat bounds upward three feet but slips back two. How long does it take for the goat to reach the top?
Spoiler:Fifty-eight minutes; he is moving at a rate of one foot per minute but once he reaches the fifty-seventh foot, he can go up three feet and hit sixty, hence fifty-eight minutes.
You have three boxes of fruit. One contains just apples, one contains just oranges, and one contains a mixture of both. Each box is labeled -- one says "apples," one says "oranges," and one says "apples and oranges." However, it is known that none of the boxes are labeled correctly. How can you label the boxes correctly if you are only allowed to take and look at just one piece of fruit from just one of the boxes?
Spoiler:Take a fruit from the box labeled "apples and oranges." Suppose you take an apple. That must mean that the box contains only apples. Therefore, the box labeled "oranges" must contain both apples and oranges, meaning the box labeled "apples" must contain oranges. "Apples and oranges" contains only apples, "apples" contains only oranges, and "oranges" contains both apples and oranges.
You have Jug A, which holds five gallons, and Jug B, which holds three gallons. You have no other containers, and there are no markings on the jugs. You need to obtain exactly seven gallons of water from a faucet. How can you do it? Bonus points if you can also find a way to obtain exactly four gallons from the same five-gallon and three-gallon jugs under the same conditions.
Spoiler:How to obtain seven gallons: Fill up Jug A, then pour three gallons of water from Jug A into Jug B. Dump out Jug B and then pour the remaining two gallons of water from Jug A into Jug B. Finally, fill up Jug A once again and you're left with seven gallons of water: five in Jug A and two in Jug B.
How to obtain four gallons: Fill up Jug B and pour all of it into Jug A. Fill up Jug B a second time and pour it into Jug A again. You're now left with five gallons in Jug A and one gallon in Jug B. Dump out all of Jug A and pour the remaining water from Jug B into Jug A. Fill up Jug B and now you have one gallon of water in Jug A and three gallons of water in Jug B, four gallons of water in total.
You have nine coins, one of them being counterfeit. The counterfeit coin has no distinguishable features aside from the fact that it is heavier than all of the other coins. You have a scale to measure the weight of the coins. What is the minimum number of measurement trials needed to distinguish the counterfeit from the rest of them?
Spoiler:Two trials; first, let's label each coin with a number. Measure coins 1, 2, and 3 against coins 4, 5, and 6. If 1, 2, and 3 are heavier, weigh 1 against 3. If either one of them is heavier, then that is the counterfeit. If they both weigh the same, then coin 2 must be the counterfeit. Use the same logic if 4, 5, and 6 are heavier than 1, 2, and 3. If 1, 2, and 3 weigh the same as 4, 5, and 6, then measure coins 7 and 8 against each other. Whichever one is heavier must be the counterfeit. If 7 and 8 weigh the same amount, then by process of elimination, coin 9 must be the counterfeit coin.
A father is four times as old as his son. In twenty years, he'll be twice as old. How old are they now?
Spoiler:The son is ten and the father is forty. In twenty years, the son will be thirty and the father will be sixty.
An explorer was trekking through a remote jungle when he was captured by logic-loving cannibals. He was brought before the chief and told, "You may now speak your last words. If your statement is true, then we will burn you at the stake. If your statement is false, we will boil you in oil." The man thought for a moment, then made his statement. Perplexed, the clever cannibals realized they could do nothing but let him go. What did the explorer tell them?
Spoiler:He said, "You will boil me in oil." If they did boil him in oil, he'd be telling them the truth, meaning they would need to burn him at the stake, which would make his last words false, which would mean he WOULD be boiled in oil, making his words true. It'd create an endless paradox, making it logically impossible for them to either burn him at the stake OR boil him in oil.
Two days ago, Suzy was 8. Next year, she'll be 11. How is this possible?
Spoiler:She was born on December 31 and "today" is January 1. Let's say she was born on December 31, 2000. Her ninth birthday is on December 31, 2009. Two days prior, she was eight. "Today" she is nine. At the end of the year she will be ten, and the next year, on December 31, 2011, she will be eleven.
The man who invented it doesn't want it. The man who bought it doesn't need it. The man who needs it doesn't know it. What is it?
Spoiler:A coffin.
Whoever makes it, tells it not. Whoever takes it, knows it not. And whoever knows it wants it not. What is it?
Spoiler:Counterfeit money.
In a small town lives two dentists: Dr. Molar and Dr. Bicuspid. Dr. Molar has perfect teeth, straight and shiny. Dr. Bicuspid has awful, crooked teeth. You need to get your teeth cleaned. Which dentist should you go to and why?
Spoiler:You should go to Dr. Bicuspid. Since there are only two dentists in town, Dr. Molar must be Dr. Bicuspid's dentist and vice-versa. Therefore, Dr. Bicuspid's terrible teeth are the result of Dr. Molar's poor dental work, and Dr. Molar's perfect teeth are the result of Dr. Bicuspid's great dental work.
A guard is stationed at the entrance to a bridge. He is tasked to shoot anyone who tries to cross to the other side of the bridge, and to turn away anyone who comes in from the opposite side of the bridge. You are on his side of the bridge and want to escape to the other side.
Because the bridge is old and rickety, anyone who tries to cross it does so at a constant speed, and it always takes exactly 10 minutes to cross. The guard comes out of his post every 6 minutes and looks down the bridge for any people trying to leave, and at all other times he sits in his post and snoozes. You know you can sneak past him when he's sleeping, but the problem is that you won't be able to make it all the way to the other side of the bridge before he sees you (since he comes out every 6 minutes, but it takes 10 minutes to cross).
One day a brilliant idea comes to you, and soon you've successfully crossed to the other side of the bridge without being shot. How did you do it?
Spoiler:Wait for the guard to go to sleep and run across the bridge for a little less than six minutes. Turn around and run back. When the guard catches you running in the direction you came, he'll think you were trying to leave rather than get in and will make you go "back" to the other side, the side you intended on being on.
In a bouquet of flowers, all but two are roses, all but two are tulips, and all but two are daisies. How many flowers are in the bouquet?
Spoiler:Three; one rose, one tulip, and one daisy.
You have two normal U.S. coins that add up to 35 cents. One of the coins is not a quarter. What are the two coins?
Spoiler:They are a dime and a quarter. The riddle says that ONE of the coins is not a quarter, not that BOTH aren't quarters. The one that is not a quarter is a dime and the other one is a quarter.
Sallie likes to eat three pieces of toast every morning before work. Unfortunately, her toaster has been malfunctioning lately and only toasts one side of each piece at a time. It takes a minute to toast each side. What is the minimum amount of time needed to toast all three pieces on both sides? (note: the toaster can toast two pieces of bread at once, but only one side of each at a time)
Spoiler:Three minutes; let's label the pieces of bread A, B, and C, and number the sides.
Minute One: Toast A1 and B1
Minute Two: Toast A2 and C1
Minute Three: Toast B2 and C2
Three men, Mr. White, Mr. Brown and Mr. Green, were in the habit of meeting in a local donut shop every morning for coffee and donuts.
One morning as they were sitting at their usual table, Mr. White remarked, "Hey, will you look at that. We're each wearing a colored baseball cap today." They were: one white cap, one brown cap, and one green cap. But interestingly, no one was wearing a cap of the color that matches his name.
At this, the guy wearing the green cap says, "That doesn't mean anything, it's just coincidence. Shut up and eat your donut."
What color cap is each man wearing?
How far can a dog run into a forest?
For the sake of this riddle, just imagine that in order to cure yourself of poisoning, you must drink a stronger poison. If you do that, both poisons will be impotent and you'll be safe. I know it makes no sense, but just pretend that it does.
In a faraway land, the king wanted to have the strongest poison in existence, in order never to be assassinated by way of poisoned drink. He summoned his alchemist, who was rumored to have the recipe to the strongest poison, and his cook. He told them that they had one week to concoct their strongest poison.
At the end of that week, they would reconvene and have a contest. Each person would drink the other person's poison, and then their own. If their poison was strongest, they would live, and the king would keep that poison. The cook knew that he would never be able to make a poison stronger than the alchemist's, so he came up with a clever plan.
When they met again before the king, the exchange of poisons took place. The cook lived, and the king didn't get what he wanted in the first place.
What was the cook's plan? How did he win the contest?
If you aim to shoot me, I'll riddle you. What am I?
[spoiler=] Bullets. Riddled with bullets, what a great expression.
In the land of Brainopia, there are three races of people: Mikkos, who tell the truth all the time, Kikkos, who always tell lies, and Zikkos, who tell alternate false and true statements, in which the order is not known (i.e. true, false, true or false, true, false). When interviewing three Brainopians, a foreigner received the following statements:
Person 1:
I am a Mikko.
Person 2:
I am a Kikko.
Person 3:
a. They are both lying.
b. I am a Zikko.
Can you help the very confused foreigner determine who is who, assuming each person represents a different race?
Spoiler:Person 1 is a Mikko, Person 2 is a Zikko, and Person 3 is a Kikko. Here's why:
To solve this, I started looking at Person 2. Since a Mikko always tells the truth and a Kikko always lies, neither of them would have claimed to be a Kikko, meaning Person 2 must be a Zikko. From there, we can determine that statement 3b is a lie. This means that Person 3 must be a Kikko, leaving Person 1 to be a Mikko. To further prove this, statement 3a states that both are lying. Knowing that Person 3 is a Kikko, we can determine that Person 1 must be telling the truth (we know that Person 2 was lying, meaning the only way statement 3a would be false was if Person 1 was telling the truth).
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