Logic Riddles

 
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Question: There are 3 men, two Chimps, and one Gorilla on one side of a river:

  • They have a boat but only the men and the Gorilla can row the boat across, so there must always be a human and/or Gorilla on the boat.
  • The boat can only carry two people/monkeys.
  • If monkeys and humans are together on one side of the river there must be as many or more people than monkeys for the men's safety.
How can all men and monkeys make it to the other side?

Answer: Steps: (They all start on the left side).
(Left side | Right side)

(3 men, 1 Gorilla, 2 Chimps | 0 men, 0 Gorilla, 0 Chimps)
-> Chimp and Gorilla (3 men, 0 Gorilla, 1 Chimps | 0 men, 1 Gorilla, 1 Chimps)
<- Gorilla (3 men, 1 Gorilla, 1 Chimps | 0 men, 0 Gorilla, 1 Chimps)
-> Chimp and Gorilla (3 men, 0 Gorilla, 0 Chimps | 0 men, 1 Gorilla, 2 Chimps)
<- Gorilla (3 men, 1 Gorilla, 0 Chimps | 0 men, 0 Gorilla, 2 Chimps)
-> Two men (1 men, 1 Gorilla, 0 Chimps | 2 men, 0 Gorilla, 2 Chimps)
<- Human and Chimp (2 men, 1 Gorilla, 1 Chimps | 1 men, 0 Gorilla, 1 Chimps)
-> Human and Gorilla (1 men, 0 Gorilla, 1 Chimps | 2 men, 1 Gorilla, 1 Chimps)
<- Human and Chimp (2 men, 0 Gorilla, 2 Chimps | 1 men, 1 Gorilla, 0 Chimps)
-> 2 men (0 men, 0 Gorilla, 2 Chimps | 3 men, 1 Gorilla, 0 Chimps)
<- Gorilla (0 men, 1 Gorilla, 2 Chimps | 3 men, 0 Gorilla, 0 Chimps)
-> Gorilla and Chimp (0 men, 0 Gorilla, 1 Chimps | 3 men, 1 Gorilla, 1 Chimps)
<- Gorilla (0 men, 1 Gorilla, 1 Chimps | 3 men, 0 Gorilla, 1 Chimps)
-> Gorilla and Chimp (0 men, 0 Gorilla, 0 Chimps | 3 men, 1 Gorilla, 2 Chimps)

And they are all safely across.

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Question: There is a brick of gold and a brick of iron in a boat (both 10 inch blocks), if they are both dropped into the water which will make the water level higher?

Hint: Gold weights more than iron.

Answer: The iron block.

The iron will make the water level higher because both blocks will actually make the water level drop most likely. In the boat they have a larger effect on the water level (raise the water level) and then when they are dropped into the water the lighter one (iron), will make the water level drop less because it is lighter and has less effect on the water from the boat but displaces the same amount of water as the gold when dropped into the water.

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Question: Tom wants to send Sally an expensive ring through the mail because they live thousands of miles apart. The only problem is that everything sent through the mail is stolen unless there is a lock put on it. Both Tom and Sally have plenty of locks and keys but they don't have any of the same locks or keys.

How can Tom send Sally the ring without it getting stolen?

Answer: Tom puts one of his locks on the box with the ring in it. When Sally gets it she puts one of her own locks on the box and sends it back to Tom. Finally Tom takes his lock off of the box and sends it back to Sally who can then unlock her own lock and retrieve the ring.

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Question: You are playing a game of dodge ball with two other people, John and Tom. You're standing in a triangle and you all take turns throwing at one of the others of your choosing until there is only one person remaining. You have a 30 percent chance of hitting someone you aim at, John has a 50 percent chance, and Tom a 100 percent change (he never misses). If you hit somebody they are out and no longer get a turn.

If the order of throwing is you, John, then Tom; what should you do to have the best chance of winning?

Answer: Miss the first time on purpose.

If you try to hit John and do. Then Tom goes next and he will hit you and you will lose for sure. If you aim at Tom and hit him then John will go for you. If you miss on your first turn John will go for Tom for sure because he is a stronger player. If he hits him then it's just you and John, but you are going first. If he misses him then Tom will hit John and it will be just you and Tom, but again in this case you are going first.

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Question: An ant gets onto one end of a tight rope that is 1 meter long. The ant is traveling at 1 centimeter per second, but the entire rope is being stretched an extra 1 meter (1,000 centimeters) a second (it can be stretched forever).

Will the ant ever reach the other end of the rope?

Answer: He will reach the end of the rope eventually. Once he gets onto the rope, the rope behind him also stretches, so this must also be accounted for.

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