Monks and Cheating Husbands

Another very popular puzzle is generally found in two variations.

Village of cheating husbands

Every man in a village of 100 married couples has cheated on his wife. Every wife in the village instantly knows when a man other than her husband has cheated, but does not know when her own husband has. The village has a law that does not allow for adultery. Any wife who can prove that her husband is unfaithful must kill him that very day. The women of the village would never disobey this law. One day, the queen of the village visits and announces that at least one husband has been unfaithful. What happens?

Island of Monks

There is an island of monks where everyone has either brown eyes or red eyes. Monks who have red eyes are cursed, and if they ever discover that they have red eyes they are supposed to commit suicide at midnight. However, no one ever talks about what color eyes they have, because the monks have a vow of silence. Also, there are no reflective surfaces on the whole island. Thus, no one knows their own eye color  they can only see the eye colors of other people. Life goes on, with brown-eyed monks and red-eyed monks living happily together in peace, and no one ever committing suicide. Then one day a tourist visits the island monastery, and during noon mass which must be attended by all monks on the island, not knowing that he’s not supposed to talk about eyes, he states the observation “At least one of you has red eyes.” Having acquired this new information, something dramatic happens among the monks. What happens?

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Hail induction

The Bridge and Flashlight Puzzle

This is very popular puzzle and most of you would have already encountered it. There are 4 men who want to cross a bridge. They all begin on the same side.You have to get all of them across to the other side in shortest time. It is night. There is only one flashlight. A maximum of two people can cross at one time. Any party who crosses, either 1 or 2 people, must have the flashlight with them. The flashlight must be walked back and forth, it cannot be thrown etc. Each man walks at a different speed. A pair must walk together at a rate of the slower man's pace. Man 1: 1 minute to cross. Man 2: 2 minutes to cross. Man 3: 5 minutes to cross. Man 4: 10 minutes to cross. For example, if Man 1 and Man 4 walk across first, 10 minutes have elapsed when they get to the other side of the bridge. If Man 4 returns with the flashlight, a total of 20 minutes have passed. So what is the shortest time and what is the sequence ?

Dog in the Circle

A man, initially placed at the center of a circle, wants to escape from the circle. Unfortunately, the circle is guarded by a vicious dog, who would eat the man. Fortunately, the dog is constrained to stay on the periphery of the circle. The dog can run up to 4 times the speed of the man, and change direction instantaneously at any time.
Can the man escape from the circle? If so, how?

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Solution