# Only 2% of People Can Solve These Brain Teasers. Can You?

#### 1. What has keys, but no locks; space, but no room; you can enter, but not go in?

Think you've cracked these brain teasers? The answers to all these puzzles will be **revealed at the end of this article/slide**. Keep **track of your guesses**, and when you're done, let us know in the comments how many you got right!

Don't forget to share this challenge with your friends and see if they can join the elite 2% who can solve them all.

**Level** : Easiest

**Hint**: Think about something you use every day for work or communication, especially when typing on a computer.

#### 2. I have cities, but no houses. I have mountains, but no trees. I have water, but no fish. What am I?

**Level** : Easiest

**Hint**: You might use this to plan a journey or locate places.

#### 3. I am an odd number. Take away a letter and I become even. What number am I?

**Level** : Easiest

**Hint**: Consider both the spelling of the number and its numerical value.

#### 4. What breaks yet never falls, and what falls yet never breaks?

**Level** : Easiest

**Hint**: Think about natural cycles and common phrases about times of day.

#### 5. Forward I am heavy, but backward I am not. What am I?

**Level** : Easiest

**Hint**: Read the word itself carefully in both directions.

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#### 6. A farmer has 10 trees. On each tree, there are 10 branches. On each branch, there are 10 nests. In each nest, there are 10 eggs. How many trees does the farmer have?

**Level** : Medium

**Hint**: Don't get distracted by the additional information. Focus on the core question.

#### 7. Two fathers and two sons went fishing. They caught three fish and each person got a whole fish. How is this possible?

**Level** : Medium

**Hint**: Consider how one person can be both a father and a son at the same time.

#### 8. If you have me, you want to share me. If you share me, you haven't got me. What am I?

**Level** : Medium

**Hint**: This is something people often struggle to keep to themselves.

#### 9. You are in a room with three light switches.

**Question : **You are in a room with three light switches. Each switch controls one of three light bulbs in another room. You can turn the switches on and off and leave them in any position. You are allowed to enter the room with the bulbs only once. How can you determine which switch controls which bulb?

**Level** : Hard

**Hint**: Think about how light bulbs react to being on for different lengths of time. Consider properties other than just whether they're lit or not.

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#### 10. You are in a room with two doors. One door leads to freedom, and the other leads to certain death

**Question**: You are in a room with two doors. One door leads to freedom, and the other leads to certain death. You don't know which door is which. There are two guards, one by each door. One guard always tells the truth, and the other always lies, but you don't know which is which. You can ask only one question to one guard to determine which door leads to freedom. What do you ask?

**Level**: Hard

**Hint**: Try to formulate a question that would force both guards to point to the same door, regardless of which one is telling the truth.

#### 11. You have two ropes. Each rope takes exactly one hour to burn from one end to the other.

**Question**: You have two ropes. Each rope takes exactly one hour to burn from one end to the other. The ropes burn non-uniformly (meaning the speed at which the flame moves along the rope is not consistent). How can you measure exactly 45 minutes?

**Level** : Hard

**Hint**: Consider how you can make one rope burn twice as fast as normal.

#### 12. Four people need to cross a bridge at night. They have one flashlight, and the bridge is too dangerous to cross without it

**Question**: Four people need to cross a bridge at night. They have one flashlight, and the bridge is too dangerous to cross without it. The bridge can only hold two people at a time. Each person walks at a different speed: 1 minute, 2 minutes, 7 minutes, and 10 minutes. When two people cross together, they must go at the slower person's pace. What is the fastest time in which all four people can cross the bridge?

**Level** : Hard

**Hint**: The fastest people should make multiple trips. Think about how to minimize the time the slowest people spend on the bridge.

#### 13. Three men are wearing hats. Each hat is either red or blue, but none of them knows the color of their own hat.

**Question**: Three men are wearing hats. Each hat is either red or blue, but none of them knows the color of their own hat. They can see the hats of the other two men but cannot communicate with each other. If a man sees that at least one of the other two men is wearing a red hat, he raises his hand. If he doesn't see a red hat, he keeps his hand down. All three men raise their hands. What color is each man's hat?

**Level**: Hardest

**Hint**: Consider what each man knows about the others' hats and what their actions reveal about their own hat color.

#### 14. You have 12 identical-looking coins, but one of them is either heavier or lighter than the others

**Question**: You have 12 identical-looking coins, but one of them is either heavier or lighter than the others. You also have a balance scale. How can you determine which coin is the odd one out and whether it is heavier or lighter using the balance scale only three times?

**Level**: Hardest

**Hint**: Start by dividing the coins into three groups. Think about how each weighing can eliminate possibilities and narrow down the location of the odd coin.

#### 15. A man walks into a room with three doors

**Question**: A man walks into a room with three doors. Behind one door is a pile of gold, behind another is a lion that hasn't eaten in three days, and behind the third is a trap that will activate as soon as the door is opened. Which door should the man choose?

**Level**: Hardest

**Hint**: Pay close attention to the specific details given about each door, especially the condition of the lion.

#### 16. The Answers / Solution

1. What has keys, but no locks; space, but no room; you can enter, but not go in?**Answer: A keyboard****Solution**: A keyboard has keys for typing, space bar, and you can enter data but not physically go in.

2. I have cities, but no houses. I have mountains, but no trees. I have water, but no fish. What am I?**Answer: A map****Solution**: Maps show cities, mountains, and bodies of water, but not their physical components.

3. I am an odd number. Take away a letter and I become even. What number am I?**Answer: Seven****Solution**: "Seven" is an odd number. Remove the 's' and it becomes "even".

4. What breaks yet never falls, and what falls yet never breaks?**Answer: Day breaks and night falls****Solution**: This is a play on common phrases about day and night.

5. Forward I am heavy, but backward I am not. What am I?**Answer: The word 'ton'****Solution**: 'Ton' is a heavy weight, but spelled backwards it's 'not'.

6. A farmer has 10 trees. On each tree, there are 10 branches. On each branch, there are 10 nests. In each nest, there are 10 eggs. How many trees does the farmer have?**Answer: 10 trees****Solution**: The question provides extra information to distract, but only asks about the number of trees.

7. Two fathers and two sons went fishing. They caught three fish and each person got a whole fish. How is this possible?**Answer: There were only three people: a grandfather, his son, and his grandson****Solution**: The middle person is both a father and a son.

8. If you have me, you want to share me. If you share me, you haven't got me. What am I?**Answer: A secret****Solution**: People want to share secrets, but once shared, it's no longer a secret.

9. You are in a room with three light switches.**Answer: Turn on one switch for a while, then turn it off and turn on another. Enter the room - the warm bulb corresponds to the first switch, the lit bulb to the second, and the cold, unlit bulb to the third.**

10. You are in a room with two doors. One door leads to freedom, and the other leads to certain death.**Answer: Ask either guard: "If I were to ask the other guard which door leads to freedom, what would he say?" Then choose the opposite door.**

11. You have two ropes. Each rope takes exactly one hour to burn from one end to the other.**Answer: Light both ends of one rope and one end of the other. When the first rope burns out (30 minutes), light the other end of the second rope. It will burn out after another 15 minutes, totaling 45 minutes.**

12. Four people need to cross a bridge at night. They have one flashlight, and the bridge is too dangerous to cross without it.**Answer: The fastest way is 17 minutes. The two fastest cross first, then the fastest returns. The two slowest cross, then the second fastest returns. Finally, the two fastest cross again.**

13. Three men are wearing hats. Each hat is either red or blue, but none of them knows the color of their own hat.**Answer: All three men are wearing red hats.**

14. You have 12 identical-looking coins, but one of them is either heavier or lighter than the others.**Answer: Use the balance scale three times, dividing the coins into groups and comparing weights to isolate the odd coin.**

15. A man walks into a room with three doors. Behind one door is a pile of gold, behind another is a lion that hasn't eaten in three days, and behind the third is a trap that will activate as soon as the door is opened.**Answer: Choose the door with the lion.****Solution**: A lion that hasn't eaten in three days would be dead, making it the safest choice.

Did you make it into the elite 2% who can solve them all? Share your results in the comments below and challenge your friends to see how they measure up!

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