Poisoned 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 to see which one he poisoned or to catch him.

The king needs the remaining 999 safe bottles for his party in 30 days. The king has 10 servants who he considers disposable. The poison takes 30 days to take effect (right before the party), and any amount of it will kill whoever drinks it. How can he figure out which bottle was poisoned in time for the party?

Einstein Logic Puzzle

There are 5 houses in a row, each with a different color. Their owners, each with a unique heritage, drinks a certain type of beverage, smokes a certain brand of cigarette, and keeps a certain variety of pet. None of the owners have the same variety of pet, smoke the same brand of cigarette or drink the same beverage.

Clues:

• The Brit lives in the red house.
• The Swede keeps dogs as pets.
• The Dane drinks tea.
• Looking from in front, the green house is just to the left of the white house.
• The green house's owner drinks coffee.
• The person who smokes Pall Malls raises birds.
• The owner of the yellow house smokes Dunhill.
• The man living in the center house drinks milk.
• The Norwegian lives in the leftmost house.
• The man who smokes Blends lives next to the one who keeps cats.
• The man who keeps a horse lives next to the man who smokes Dunhill.
• The owner who smokes Bluemasters also drinks beer.
• The German smokes Prince.
• The Norwegian lives next to the blue house.
• The man who smokes Blends has a neighbor who drinks water.

Who owns the pet fish?

100 Prisoners and a Lightbulb

There are 100 prisoners in a jail, each in an isolated cell. In the lobby of the jail is a room with a light and a lightbulb (starts in the off position), which can only been seen from the lobby. Each day, the warden will take 1 random prisoner down to the lobby. The prisoner can flip the switch (either turning the bulb off it was on or on if it was off), or the prisoner can do nothing, or the prisoner can say "each prisoner has been to the lobby at least once." If the prisoner who says this is correct, they all go free. If he is incorrect, they are all killed. The prisoners can get together at the very beginning to discuss a strategy, but can not communicate with one another ever again until the exercise is over. What strategy can the prisoners use to guarantee that they all survive?

1 Million Lockers

There are one million numbered lockers in a row. They all start out closed. On your first pass, you flip every locker, so each one is open. On your second pass, you flip every locker divisible by 2, so you close lockers 2, 4, 6, etc. On the third pass, you flip every locker divisible by 3, so locker 3 becomes closed, locker 6 becomes open, etc. You continue this pattern until the millionth pass, flipping only the millionth locker on the last pass. At the end, is the millionth locker open? What do all the open lockers have in common? Why?

Trains

There are two trains traveling 60 mph towards each other. When they are 120 miles apart, a fly leaves one train heading towards the other at 100 mph. As soon as it reaches the other train, it immediately flies back towards the first train. It continues doing this until the trains collide. How much distance does the fly cover before the trains collide?

Cards in the Dark

You are in a completely dark room with a deck of 52 cards. 12 of the cards are face up, but they are randomly distributed throughout the deck. You need to put the cards into two piles (not necessarily of the same size) so that each pile has the same number of face up cards. There are no markings on the cards that would help you identify the face up cards in any way. You can also flip cards to upside down if you want (changing the number of total face up cards). How do you do it?

25 Horses

You have 25 horses. You need to find out which 3 are the fastest. Only 5 horses can race at a time. You are only given the order in which the horses finish the races, not their actual times. What is the fewest number of races you need to find the 3 fastest?

Gameshow and Urns

You are on a game show. You have 50 Red and 50 Green balls and 2 urns. You are free to distribute the balls among the 2 urns anyway you want. The host then randomly picks an urn and then randomly picks a ball from that urn. A Green ball means you win $1 MM, a Red ball or no ball means you win nothing. How should you distribute the 100 balls?

7 Days of Work

You have one block of gold, weighing 7 pounds. You also have a worker, who is going to work for you for 7 days. You need to pay him 1 pound of gold a day. You can only make 2 cuts into the block of gold. How would you make the cuts so that you can pay 1 pound of gold for each day worked?

50 Prisoners and Hats

A king has fifty prisoners. He decides to play a game to give them a chance to win their freedom. The next day, he will line up the prisoners in a straight line, all facing the same direction. He will then place either a white hat or a black hat on each of their heads. There is no pattern to how he will place the hats and there is no known set number of each color hat. He could choose any number of black hats and any number of white hats, as long as each prisoner has a hat on his head. Once in a line, the prisoner at the back can see all the hats in front of him, and the prisoner in the front can not see any of the hats. The king will start at the back and allow the last prisoner to guess his hat color. He can only say "white" or "black", and he can not signal with timing, pitch, hand motions, etc. Only "white" or "black" in a monotone voice, or they will all be killed. If the prisoner guesses correctly, he will be set free. If not, he will be killed and the king will move forward to the next prisoner in line. He will continue this way all the way down until all the prisoners have attempted to guess their hat color. During the exercise, each prisoner can hear what happens to all the prisoners behind him (whether each lives or dies). The night before, the prisoners meet together and come up with a strategy where at MOST, one of them will die. What is this strategy that guarantees to save at least 49 of them?