RIDDLES
Riddle: How Many Birds Remain?
Imagine a tree with 100 birds perched on its branches. You throw a stone and manage to hit 2 birds. How many birds are left on the tree?
Answer:
click below
If you throw a stone and hit 2 birds, they will fly away. But the noise and commotion will likely cause all the other birds to fly away as well. So, the answer is that no birds will remain on the tree.
Riddle: I’m tall when I’m young, and I’m short when I’m old. What am I?
Riddle: What month of the year has 28 days?
Riddle: What is full of holes but still holds water?
Riddle: What goes up but never comes down?
Answer1: A candle.
Answer2: All of them.
Answer3: A sponge.
Answer4: Your age.
These logic puzzles can provide hours of mental exercise and are great for developing critical thinking and problem-solving skills. Enjoy the challenge!
1. The Classic River Crossing Puzzle
Three humans and three monsters need to cross a river using a boat that can carry only two creatures at a time. If the monsters ever outnumber the humans on either side of the river, the monsters will eat the humans. How can they all get across the river safely?
2. The Three Houses and Utilities Puzzle
Draw three houses and three utility companies (water, electricity, gas). Connect each house to each utility without crossing any lines.
3. The Four-Digit Number Puzzle
Find a four-digit number in which the first digit is one-third of the second digit, the third digit is the sum of the first and second digits, and the fourth digit is three times the second digit.
4. The Five-Door Logic Puzzle
You are in a room with five doors. One door leads to freedom, and the other four lead to traps. You have a robot that can test one door at a time. The robot will either return to you safely (indicating a trap) or not return (indicating the correct door). How can you ensure that you find the door to freedom?
5. The Two-Guard Door Puzzle
You are in a room with two doors. One door leads to freedom, the other to certain death. There are two guards, one always tells the truth, the other always lies. You can ask one guard one question to determine the door to freedom. What do you ask?
6. The 12 Coin Problem
You have 12 coins, one of which is either heavier or lighter than the others. You have a balance scale and can use it three times. Determine which coin is the different one and whether it is heavier or lighter.
7. The Bridge and Torch Problem
Four people need to cross a bridge at night. They have one torch, and the bridge is too dangerous to cross without it. Only two people can cross at a time. Each person walks at a different speed: 1 minute, 2 minutes, 5 minutes, and 10 minutes. How can they all cross the bridge in 17 minutes?
8. The Five Hats Puzzle
Five people are standing in a line, each wearing a hat that is either red or blue. Each person can see the hats of the people in front of them but not their own or those behind them. They must guess the color of their own hat. Starting from the last person in the line and moving forward, how can they maximize the number of correct guesses?
9. The Light Switch Puzzle
You are outside a room with three light switches. Inside the room, there are three light bulbs. Each switch controls one bulb, and you cannot see the bulbs from outside. How can you determine which switch controls which bulb if you can enter the room only once?
10. The Knight and Knave Puzzle
On an island, there are knights (who always tell the truth) and knaves (who always lie). You meet two inhabitants: A and B. A says, “At least one of us is a knave.” What are A and B?
1. The Classic River Crossing Puzzle
Solution:
1. Take two monsters across the river. (M, M)
2. Bring one monster back. (M)
3. Take two monsters across the river. (M, M)
4. Bring one monster back. (M)
5. Take two humans across the river. (H, H)
6. Bring one monster and one human back. (M, H)
7. Take two humans across the river. (H, H)
8. Bring one monster back. (M)
9. Take two monsters across the river. (M, M)
2. The Three Houses and Utilities Puzzle
Solution: This puzzle is impossible to solve on a flat plane without lines crossing. It is known as a problem without a solution in two dimensions.
3. The Four-Digit Number Puzzle
Solution: The number is 1346.
– First digit (1) is one-third of the second digit (3).
– Third digit (4) is the sum of the first and second digits (1+3).
– Fourth digit (6) is three times the second digit (3).
4. The Five-Door Logic Puzzle
Solution: Test one door at a time. If the robot returns, it’s a trap. If the robot does not return, that’s the door to freedom. Repeat for the remaining doors until you find the door to freedom.
5. The Two-Guard Door Puzzle
Solution:Ask either guard, “If I were to ask the other guard which door leads to freedom, what would they say?” Then choose the opposite door.
6. The 12 Coin Problem
Solution:
1. Divide the 12 coins into three groups of 4 coins each.
2. Weigh group 1 against group 2.
3. If balanced, the odd coin is in group 3. If not, the odd coin is in the heavier or lighter group.
4. Take the heavier/lighter group and divide into two groups of 2 coins each.
5. Weigh one group against the other.
6. The heavier/lighter group contains the odd coin.
7. Weigh one coin from the remaining group against another coin.
8. The heavier/lighter coin is the odd coin.
7. The Bridge and Torch Problem
Solution:
1. First, Person 1 and Person 2 cross the bridge. (2 min)
2. Person 1 returns with the torch. (1 min, Total: 3 min)
3. Person 3 and Person 4 cross the bridge. (10 min, Total: 13 min)
4. Person 2 returns with the torch. (2 min, Total: 15 min)
5. Finally, Person 1 and Person 2 cross the bridge again. (2 min, Total: 17 min)
8. The Five Hats Puzzle
Solution:
1. The last person (5th) will count the number of red hats they see.
2. If they see an even number of red hats, they say “red” if they themselves have a red hat.
3. If they see an odd number of red hats, they say “blue”.
4. Each subsequent person uses the previous answers to deduce their hat color.
9. The Light Switch Puzzle
Solution:
1. Turn on the first switch and leave it on for a few minutes.
2. Turn off the first switch and turn on the second switch.
3. Enter the room.
4. The bulb that is on is controlled by the second switch.
5. The bulb that is off but warm is controlled by the first switch.
6. The bulb that is off and cold is controlled by the third switch.
10. The Knight and Knave Puzzle
Solution:
If A says, “At least one of us is a knave,” A must be telling the truth, making A a knight and B a knave. If A were a knave, then the statement would be false, which contradicts the scenario of having at least one knave. Thus, A is a knight and B is a knave.
I hope these solutions help clarify the puzzles!