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20 Challenging Brain Teasers with Answers

Last Updated : 21 Dec, 2023
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Brain teasers are puzzles or problems that are designed to stimulate and challenge the brain. They often require creative thinking, problem-solving skills, and the ability to think outside the box. Brain teasers come in various forms, including riddles, puzzles, and logic games. They are a fun way to exercise the mind and enhance cognitive abilities.

20 Challenging Brain Teasers with Answers

Here are 20 challenging brain teasers along with their answers. Try to solve them before checking the answers:

1. The Missing Dollar: Three people check into a hotel room that costs $30. They each contribute $10, handing $30 to the hotel clerk. Later, the hotel clerk realizes that there was a mistake, and the room only costs $25. The hotel clerk gives $5 to the bellboy and asks him to return it to the guests. However, the bellboy decides to keep $2 for himself and gives $1 back to each guest. Now, each guest has paid $9 (totalling $27) and the bellboy has kept $2, making $29. What happened to the missing dollar?

2. The Two Doors: You are in a room with two doors. One door leads to certain death, and the other door leads to freedom. There are two guards, one in front of each door. One guard always tells the truth, and the other always lies. You don’t know which guard is which, and you don’t know which door leads to freedom. You can ask one guard one yes-or-no question. What do you ask to find the door to freedom?

3. The Poisoned Wine: You are a king and have 1,000 bottles of wine. One of the bottles contains poison, and anyone who drinks it will die within 24 hours. You have 10 prisoners whom you suspect might try to assassinate you. You decide to find the poisoned bottle of wine by feeding it to the prisoners. You have only 24 hours to determine which bottle is poisoned. How do you do it?

4. The Escalator: If an escalator is moving down, is it easier or harder to walk down?

5. The Lockers: There are 100 lockers in a row, all initially closed. A person walks down the row and opens every locker. Then, another person walks down the row and closes every second locker (starting from the second locker). Next, a third person walks down the row and changes the state (opens it if it’s closed or closes it if it’s open) of every third locker (starting from the third locker). This continues until 100 people have walked down the row. At the end, which lockers are open?

6. The Unfinished Statement: Can you complete the following statement: “I am the beginning of the end and the end of time and space. I am essential to creation, and I surround every place. What am I?”

7. The Three Switches: You are in a room with three light switches. Each switch controls one of three bulbs in the next room. You can’t see into the next room, and once you leave the room, you can’t come back. How can you determine which switch controls which bulb?

8. The Clock Chimes: A clock chimes 5 times in 4 seconds. How many times will it chime in 10 seconds?

9. The Two Fathers and Two Sons: A father and a son go on a fishing trip. They each catch one fish. In total, there are only three fish. How is this possible?

10. The Greenhouse: You are in a greenhouse. There are five greenhouses. In each greenhouse, there are five cats. In each cat, there are five kittens. How many legs are there in total?

11. The Man in the Bar: A man walks into a bar and asks the bartender for a glass of water. The bartender pulls out a gun and points it at the man. The man says, “Thank you,” and walks out. What happened?

12. The Train Journey: A train leaves from New York City heading to Los Angeles at 150 miles per hour. At the same time, a train leaves from Los Angeles heading to New York City at 200 miles per hour. Which train will be farther from New York City when they meet?

13. The Running Race: If you overtake the last person in a running race, what place are you in?

14. The Word That Is Spelled Incorrectly: What is the only word that is spelt incorrectly in the dictionary?

15. The Pink House: In a one-story pink house, there was a pink person, a pink cat, a pink fish, a pink computer, a pink chair, a pink table, a pink phone, a pink shower – everything was pink! What color were the stairs?

16. The Murder Mystery: A man was found murdered on Sunday morning. His wife immediately called the police. The police questioned the wife and staff and got the following alibis:

  • The wife said she was sleeping.
  • The cook said he was cooking breakfast.
  • The gardener said he was planting seeds.
  • The maid said she was getting the mail.
  • The butler said he was polishing the silverware.

The police arrested the murderer immediately. Who was it?

17. Cowboy: A cowboy arrives in town on Friday, stays for three days, and then leaves on Friday. How did he do it?

18. The Deadly Party: A man went to a party and drank some of the punch. He then left early. Everyone else at the party who drank the punch died of poisoning. Why did the man not die?

19. The Two Men in Masks: Two men were born in the same year, on the same day, in the same city, and they have the same parents. However, they are not twins. How is this possible?

20. Bankruptcy: A man pushes his car to a hotel and tells the owner he’s bankrupt. Why?

Answers:

1. There is no missing dollar. The guests have paid a total of $27 ($25 to the hotel and $2 to the bellboy).

2. Ask either guard, “If I were to ask the other guard which door leads to freedom, what would he say?” Then choose the opposite of the answer.

3. Label the bottles from 1 to 1,000 in binary. Feed each prisoner a mix of wine from bottles where the corresponding binary digits are 1 in their number. For example, prisoner 1 gets wine from bottles with a binary representation that has a 1 in the rightmost digit, prisoner 2 gets wine from bottles with a 1 in the second rightmost digit, and so on. If a prisoner dies, the binary representation of the bottle number will reveal the poisoned bottle.

4. Easier. Escalators are designed to assist walking, so if it’s moving down, it reduces the effort required to walk down.

5. The lockers that are open are the perfect squares: 1, 4, 9, 16, …, 100.

6. The letter ‘E.’

7. Turn on one switch and leave it on for a few minutes. Then, turn it off and turn on another switch. Enter the room. The bulb that is on corresponds to the switch that is on. The bulb that is off and warm corresponds to the switch that was turned on and off. The bulb that is off and cool corresponds to the switch that was never turned on.

8. The clock will chime 12 times in 10 seconds.

9. The fishing party consists of a grandfather, his son, and his grandson.

10. There are 14 legs. Each cat has four legs, and the person (you) has two legs.

11. The man had the hiccups. The bartender scared him, causing the hiccups to stop.

12. They will be at the same distance from New York City when they meet.

13. If you overtake the last person, you take their place, so you are in the last place.

14. The word “incorrectly.”

15. There were no stairs. It was a one-story house.

16. The maid. There is no mail on Sunday.

17. His horse was Friday.

18. The poison was in the ice. When the man drank the punch, the ice had not melted yet.

19. They are two of a set of triplets.

20. The man is playing Monopoly. He landed on a property with a hotel, couldn’t pay the rent, and declared bankruptcy.



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