Browsing the archives for the puzzle tag

Bulb Or No Bulb?

Question: There are 100 bulbs arranged in a row. Each bulb has its own switch and is currently turned off.  In the first round, you turn every switch on. In the second round, you flip the switch of every second bulb (i.e. bulb 2, 4, 6, 8 and so on). In the third round, you […]

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What’s Your Eye Color?

Question: 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 […]

9 Comments

How Strong is an Egg?

Question: You have two identical eggs. Standing in front of a 100 floor building, you wonder what is the maximum number of floors from which the egg can be dropped without breaking it. What is the minimum number of tries needed to find out the solution? Answer: The easiest way to do this would be […]

81 Comments

Is Your Husband a Cheat?

Question: A certain town comprises of 100 married couples. Everyone in the town lives by the following rule: If a husband cheats on his wife, the husband is executed as soon as his wife finds out about him. All the women in the town only gossip about the husbands of other women. No woman ever tells […]

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How Old Are My Children?

Question: Two old friends, Jack and Bill, meet after a long time. Jack: Hey, how are you man? Bill: Not bad, got married and I have three kids now. Jack: That’s awesome. How old are they? Bill: The product of their ages is 72 and the sum of their ages is the same as your […]

22 Comments

5 Pirates Fight for 100 Gold Coins

Question: Five pirates discover a chest containing 100 gold coins. They decide to sit down and devise a distribution strategy. The pirates are ranked based on their experience (Pirate 1 to Pirate 5, where Pirate 5 is the most experienced). The most experienced pirate gets to propose a plan and then all the pirates vote […]

Four People on a Rickety Bridge

Question: Four people need to cross a rickety bridge at night. Unfortunately, they have only one torch and the bridge is too dangerous to cross without one. The bridge is only strong enough to support two people at a time. Not all people take the same time to cross the bridge. Times for each person: […]

26 Comments

Apples and Oranges?

Question: You have 3 baskets, one with apples, one with oranges and one with both apples and oranges mixed. Each basket is closed and is labeled with ‘Apples’, ‘Oranges’ and ‘Apples and Oranges’. However, each of these labels is always placed incorrectly. How would you pick only one fruit from a basket to place the […]

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Trailing Zeros in 100 Factorial

Question: How many zeros are there in 100! (100 factorial)? Answer: For those who don’t know what factorial is, 100! = 100 * 99 * 98 * … * 2 * 1 Ok, let’s look at how trailing zeros are formed in the first place. A trailing zero is formed when a multiple of 5 is multiplied […]

6 Comments

100 Prisoners in Solitary Cells

Question: 100 prisoners are stuck in the prison in solitary cells. The warden of the prison got bored one day and offered them a challenge. He will put one prisoner per day, selected at random (a prisoner can be selected more than once), into a special room with a light bulb and a switch which controls the […]