12 Logic Puzzles That Will Test Your Smarts

Think your brain is up for a challenge? Logic puzzles are a fun and clever way to boost your critical thinking, attention to detail, and problem-solving skills. Whether you're a riddle rookie or a seasoned puzzle pro, these 12 brain teasers are sure to stretch your mind—and maybe even stump you.

Let’s see how many you can solve!

1. The Missing Dollar

Three friends split a $30 bill evenly. They each pay $10. Later, the cashier realizes the bill was only $25 and gives $5 back. Since $5 can’t be split evenly, the waiter gives each friend $1 and keeps $2.Now each friend paid $9 ($27 total) and the waiter has $2—where’s the missing dollar?

Answer: There’s no missing dollar. The $27 includes the $25 bill and the $2 the waiter kept. The trick is in the way the question is phrased.

2. The Two Doors

You’re in a room with two doors. One leads to certain death, the other to freedom. Each door has a guard. One always tells the truth, the other always lies. You can ask one question to one guard. What do you ask?

Answer: Ask either guard: “If I asked the other guard which door leads to freedom, what would he say?” Then, take the opposite door.

3. The Light Bulb Riddle

You're outside a room with three light switches. One switch controls a bulb inside the room. You can only enter the room once. How do you find out which switch controls the bulb?

Answer: Turn on one switch for a few minutes, then turn it off. Turn on the second one. Enter the room: the lit bulb is switch #2, the warm but off bulb is #1, and the cold bulb is #3.

4. The Fox, Chicken, and Grain

You have to cross a river with a fox, a chicken, and a bag of grain. Your boat can only carry you and one item. If left alone, the fox eats the chicken, and the chicken eats the grain. How do you get all across safely?

Answer:

1. Take the chicken over.

2. Go back alone.

3. Take the fox over.

4. Bring the chicken back.

5. Take the grain over.

6. Return alone.

7. Take the chicken over.

   
   

5. The Stolen Necklace

A man is accused of stealing a necklace. He says, “I didn’t steal it. The day it was taken, I was wearing a red shirt.” But the security camera footage shows the thief in a blue shirt. What’s off about his defense?

Answer: He never should’ve known what day the necklace was stolen if he’s innocent.

6. Who’s the Liar?

Four people are suspected of cheating on a test. One of them is guilty.

• Alice says: “It wasn’t me.”

• Bob says: “It was Daniel.”

• Charlie says: “It was Bob.”

• Daniel says: “Charlie lied.”

If only one is telling the truth, who’s the cheater?

Answer: Charlie. If Charlie is telling the truth, Bob is guilty—but then Bob’s statement (that it was Daniel) would be false, which fits. All others would be lying.

7. The Poisoned Drink

A woman ordered a drink at a party. She drank it slowly. Several others drank the same beverage quickly—and died. Why did she survive?

Answer: The poison was in the ice. She drank slowly, and the ice had time to melt. The others drank before it melted.

8. Three Switches and a Fan

A fan has three switches. Only one turns it on. You flip all three switches, one at a time, but the fan only starts spinning after a short delay. How do you find the correct switch?

Answer: Flip one switch, wait. Turn it off. Flip the second and wait. If the fan starts later, it's the second. If not, it was the first. If nothing, it’s the third.

9. The Calendar Problem

What occurs once in a minute, twice in a moment, and never in a thousand years?

Answer: The letter "m".

10. Truth or Lie

You’re walking in a forest and come across a fork. One path leads to safety, the other to danger. At the fork stands someone who either always lies or always tells the truth. You don’t know which. What do you ask?

Answer: Ask, “If I asked you which way is safe, what would you say?” Then take that direction.

11. Age Puzzle

Two years ago, a father was three times as old as his son. In four years, he’ll be twice as old. How old are they now?

Answer: The son is 10, the father is 30.

12. Who Died First?

Two people are lying dead in a room. There’s broken glass and water on the floor. How did they die?

Answer: They were goldfish. The bowl broke, spilling water and killing them.

Final Thoughts

Some of these logic puzzles test math skills, others your ability to see past distractions. If you enjoyed these, challenge your friends or try creating one of your own. And remember—every time you solve a puzzle, your brain gets stronger.

Keep sharpening your mind with more clever content right here on MindMatter.