Lucretia Borgia invited a prospective victim to lunch. They ate a hearty meal of roast venison, with a selection of fresh vegetables, all washed down with the finest wine imported from Bordeaux in France. After the meal they finished off with figs and grapes freshly picked. “Just one apple left”, said Lucretia, “I insist you have that. “No”, said the guest, “I couldn’t”. “Tell you what”, said Lucretia, “we will share it”, and promptly sliced it neatly in two with her sharpest knife. The guest and Lucretia started to eat their respective halves when suddenly the guest’s eyes rolled towards the ceiling and he keeled over backwards stone dead. “Another victim successfully despatched,” thought Lucretia. Why was Lucretia not poisoned after eating the apple?

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Once upon a time, in the West Lake village, a servant lived with his master. After service of about 30 years, his master became ill and was going to die. One day, the master called his servant and asked him for a wish. It could be any wish but just one. The master gave him one day to think about it. The servant became very happy and went to his mother for discussion about the wish. His mother was blind and she asked her son for making a wish for her eye-sight to come back. Then the servant went to his wife. She became very excited and asked for a son as they were childless for many years. After that, the servant went to his father who wanted to be rich and so he asked his son to wish for a lot of money. The next day he went to his master and made one wish through which all the three (mother, father, wife) got what they wanted. What was the servant’s wish?

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On a certain island there are people with assorted eye colors. There are 100 people with blue eyes and 100 people with brown eyes. Since there are no mirrors on this island, no person knows the color of their own eyes. The people on the island are not allowed to talk or communicate with each other in any way. They are also not aware of the number of blue or brown eyed people on the island. For all they know, they could have red eyes too. But they are allowed to observe other people and keep count of the number of people with a certain eye color. There is a rule that the people on the island have to follow – any person who is sure of their eye color has to leave the island immediately. One day, a person comes to the island and announces to the people that he sees someone with blue eyes. Everyone knows that the person only speaks the truth. What do you think happens?

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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?

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A Japanese ship was en route in the open sea. The Japanese captain went for a shower removing his diamond ring and Rolex watch on the table. When he returned, his valuables were missing. The captain immediately called the five suspected crew members and asked each one where and what he was doing for the last 15 minutes. The Filipino cook in a heavy overcoat said, “I was in fridge room getting meat for cooking.” The Indian Engineer with a torch in hand said, “I was working on generator engine.” The Sri Lankan seaman said, “I was on the mast (top of the ship) correcting the flag which was upside down by mistake.” The British radio officer said, “I was messaging to company that we are reaching the next port in 72 hours. From now that is Wednesday morning at 10 AM. The British navigation officer said, “I am on night watch, so sleeping in my cabin.” The captain caught the liar. So who is the thief?

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A friend of mine emptied a box of matches on the table and divided them into three heaps, while we stood around him wondering what he was going to do next. He looked up and said, “Well friends, we have here three uneven heaps. Of course you know that a match box contains altogether 48 matches. This I don’t have to tell you. And I am not going to tell you how many there are in each heap.” “What do you want us to do?” one of the men shouted. “Look well, and think. If I take off as many matches from the first heap as there are in the second and add them to the second, and then take as many from the second as there are in the third and add them to the third, and lastly if I take as many from the third as there are in the first and add them to the first—then the heaps will all have equal number of matches.” As we all stood there puzzled he asked, “Can you tell me how many were there originally in each heap?” Can you?

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This puzzle has been said to have been invented by Albert Einstein as a boy and some claim that only 2% of the population can solve it. There are 5 houses in 5 different colors. All the 5 owners are of different nationality. The 5 owners drink different beverages, smoke different brand of cigars, and own different pets. No owners have the same pet, smoke the same brand of cigar, or drink the same beverage. There are five houses. The Brit lives in the red house. The Spaniard owns the dog. Coffee is drunk in the green house. The Ukrainian drinks tea. The green house is immediately to the right of the ivory house. The Old Gold smoker owns snails. Kools are smoked in the yellow house. Milk is drunk in the middle house. The Norwegian lives in the first house. The man who smokes Chesterfields lives in the house next to the man with the fox. Kools are smoked in the house next to the house where the horse is kept. The Lucky Strike smoker drinks orange juice. The Japanese smokes Parliaments. The Norwegian lives next to the blue house. Who owns the zebra?

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The King calls in three wise men and tells them to all close their eyes. While their eyes are closed, he goes around and puts a hat on each of them. “I put a blue or white hat on each of you,” the King says. “I won’t tell you what color each hat is, but I promise you that at least one of you has a blue hat.” “Now open your eyes,” he continues. “You may not communicate with each other at all. Within one hour, one of you must call out the color of your own hat. If you aren’t able to do this, or if anyone calls out the wrong color, I will have you all exiled from the kingdom.” The wise men open their eyes and look at the other mens’ hats. They stand there for almost the whole hour in silence, thinking. Just as time is about to run out, all three men figure out the color of their own hats and yell the colors out at the same time. You can assume that all three men are perfect logicians, that they know that the others are perfect logicians, and that they all think at the same speed. What colors are the three men’s hats?

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There are 1 million closed school lockers in a row, labeled 1 through 1,000,000. You first go through and flip every locker open. Then you go through and flip every other locker (locker 2, 4, 6, etc…). When you’re done, all the even-numbered lockers are closed. You then go through and flip every third locker (3, 6, 9, etc…). “Flipping” mean you open it if it’s closed, and close it if it’s open. For example, as you go through this time, you close locker 3 (because it was still open after the previous run through), but you open locker 6, since you had closed it in the previous run through. Then you go through and flip every fourth locker (4, 8, 12, etc…), then every fifth locker (5, 10, 15, etc…), then every sixth locker (6, 12, 18, etc…) and so on. At the end, you’re going through and flipping every 999,998th locker (which is just locker 999,998), then every 999,999th locker (which is just locker 999,999), and finally, every 1,000,000th locker (which is just locker 1,000,000). At the end of this, is locker 1,000,000 open or closed?

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Five potential donors are sitting on a bench from left to right outside the surgery room and are waiting for the doctor. Their ages are 6, 10, 31, 47 and 61. Their heights are 41, 49, 61, 66 and 75 inches. Their weights are 41, 76, 97, 126 and 166 pounds. Determine the position, blood group, age, height and weight of each of them with the help of the following ten hints. The person on the far right is 37 years older than Jimmy, and is 61 inches tall. Jimmy weighs 56 pounds more than his height. Alexandrio weighs 76 pounds and is 75 inches tall. Justin is type AB and weighs 56 pounds less than Jimmy. The person in the center is 10 years old, is blood type AO and weighs 97 pounds. Andrew, who is the first, is 66 inches tall, and weighs 100 pounds more than his height. The person who is blood type O, is 25 years older than the person to the left of them. Kian is 61 years old. The person who is blood type A, is 55 years younger than Kian and is not next to the person who is type AO. The person who is next to the 10 year old but not next to the person who is 66 inches tall, is blood type B, and weighs 126 pounds.

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Three Gods A, B, and C are called, in no particular order, True, False, and Random. True always speaks truly, False always speaks falsely, but whether Random speaks truly or falsely is a completely random matter. Your task is to determine the identities of A, B, and C by asking three yes-no questions; each question must be put to exactly one God. The Gods understand English, but will answer all questions in their own language, in which the words for yes and no are “da” and “ja”, in some order. You do not know which word means which. It could be that some God gets asked more than one question (and hence that some God is not asked any question at all). What the second question is, and to which God it is put, may depend on the answer to the first question. (And of course similarly for the third question.) Whether Random speaks truly or not should be thought of as depending on the flip of a coin hidden in his brain: if the coin comes down heads, he speaks truly; if tails, falsely. Random will answer “da” or “ja” when asked any yes-no question. What would your three questions be?

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A king has 100 identical servants, each with a different rank between 1 and 100. At the end of each day, each servant comes into the king’s quarters, one-by-one, in a random order, and announces his rank to let the king know that he is done working for the day. For example, servant 14 comes in and says, “Servant 14, reporting in.” One day, the king’s aide comes in and tells the king that one of the servants is missing, though he isn’t sure which one. Before the other servants begin reporting in for the night, the king asks for a piece of paper to write on to help him figure out which servant is missing. Unfortunately, all that’s available is a very small piece that can only hold one number at a time. The king is free to erase what he writes and write something new as many times as he likes, but he can only have one number written down at a time. The king’s memory is bad and he won’t be able to remember all the exact numbers as the servants report in, so he must use the paper to help him. How can he use the paper such that once the final servant has reported in, he’ll know exactly which servant is missing?

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One day, a father went to his three sons and told them that he would die soon and he needed to decide which one of them to give his property to. He decided to give them all a test. He said, “Go to the market my sons, and purchase something that is large enough to fill my bedroom, but small enough to fit in your pocket. From this I will decide which of you is the wisest and worthy enough to inherit my land.” So they all went to the market and bought something that they thought would fill the room, yet was still small enough that they could fit into their pockets. Each son came back with a different item. The father told his sons to come into his bedroom one at a time and try to fill up his bedroom with whatever they had purchased. The first son came in and put some pieces of cloth that he had bought and laid them end to end across the room, but it barely covered any of the floor. Then the second son came in and laid some hay, that he had purchased, on the floor but there was only enough to cover half of the floor. The third son came in and showed his father what he had purchased and how it could fill the entire room yet still fit into his pocket.The father replied, “You are truly the wisest of all and you shall receive my property.” What was it that the son had showed to his father?

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Four prisoners named P1, P2, P3 and P4 are arrested for a crime, but the jail is full and the jailer has nowhere to put them. He eventually comes up with the solution of giving them a puzzle and if they answer correctly they can go free but if they fail they are to be executed. The jailer makes prisoners P1, P2 and P3 stand in a single file. Prisoner P4 is put behind a screen. The arrangement looks like this: P1 P2 P3 || P4 The ‘||’ is the screen. The jailer tells them that there are two black hats and two white hats; that each prisoner is wearing one of the hats; and that each of the prisoners is only able to see the hats in front of them but not on themselves or behind. Prisoner P1 can see P2 and P3. Prisoner P2 can see P3 only. The fourth man, P4, behind the screen can’t see or be seen by any other prisoner. No communication between the prisoners is allowed. If any prisoner can figure out and tell the jailer the color of the hat he has on his head all four prisoners go free. If any prisoner gives an incorrect answer, all four prisoners are executed. How the prisoners can escape, regardless of how the jailer distributes the hats? You can assume that the prisoners can all hear each other if one of them tries to answer the question. Also, every prisoner thinks logically and knows that the other prisoners think logically as well.

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Once upon a time there was a kingdom. A king and a clown lived in this kingdom. Unfortunately they hated each other so they agreed that they will poison each other one day. There are only twelve vials of poison in whole kingdom and they are locked in one chamber in the castle. The poisons have numbers from 1 to 12. The higher the number the stronger the poison. The effect on the human body is simple – you drink the poison, you die. Each stronger poison neutralizes all weaker poisons which means that poison 12 neutralizes all poisons, poison 11 neutralizes all poisons except poison 12, etc. If you drink poison 11 followed by poison 12 nothing happens. If you drink poison 12 and then poison 11 you die. The king enters the chamber first and takes all the even numbered poisons (2, 4, 6, 8, 10, 12). The clown then enters and takes the odd numbered poisons. They meet in the throne hall where each fills one cup and hands it over to the other who immediately drinks it. Now each fills the cup once again, now for himself, and drinks it (hoping to save his own life). Both the king and the clown primarily want to survive but want to poison the other. There is one dose of each poison – it’s not possible to divide it. The poisons are fluids without color or smell and they have the same consistency as water. The clown survived and the king died from the poison. What did the clown do?

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