Riddles That Make You Think With Answers
Updated · Best Riddles With Answers editorial team
Quick answer: These 42 riddles that make you think go beyond quick guesses. Some ask what an idea is, such as memory, hope or a habit. Others are thought experiments about sound, ships, maps and speed. Every one has an answer with a short explanation, so you can see how the thinking works.
Easy Riddles That Make You Think
I show you everything you look like, yet I cannot say a word, and I always swap your left and right. What am I?
A mirror.
I am a room with no walls where yesterday is stored. I grow dim if I am neglected and sharper the more I am used. What am I?
Memory.
I begin when your eyes close and end when they open, and no one else can see me. What am I?
A dream.
I was the last thing left in Pandora's jar after every trouble escaped. What am I?
Hope.
I am the only day you can learn from but never visit. What am I?
Yesterday.
I am built by what you do, held by what others say, and I walk into the room before you do. What am I?
Your reputation.
I am easy to make and hard to break, and I am built from repetition. What am I?
A habit.
I am made many times a day, and even refusing to make me is one of me. What am I?
A decision (a choice).
I always arrive just after I am needed. What am I?
Experience.
I travel anywhere in an instant without moving, and I cannot be seen or weighed. What am I?
A thought.
I am bitter at the root and sweet in the fruit, and I am tested by waiting. What am I?
Patience.
I grow when you feed me attention and shrink when you face me. What am I?
Fear.
Trickier Riddles That Make You Think
If a tree falls in a forest and no one is there to hear it, does it make a sound?
It makes sound waves, but nobody experiences a sound. The answer depends on whether sound means vibrations in the air or the hearing of them.
A ship has every plank replaced, one at a time, until none of the original wood remains. Is it still the same ship?
It depends on what makes a ship the same. If it is the shape and continuous use, yes. If it is the original material, no.
Which came first, the chicken or the egg?
The egg. Birds that were almost chickens laid eggs, and in one of those eggs the first true chicken hatched.
A glass is filled with water to the halfway mark. Is it half full or half empty?
Both are accurate. People tend to say half full if it was being filled, and half empty if it was being drained.
What happens when an unstoppable force meets an immovable object?
They cannot both exist. If a force is truly unstoppable, nothing is immovable, and the reverse is also true.
A mirror seems to swap left and right but not up and down. Why?
It really swaps front and back. Left and right seem to flip because we imagine turning around to stand where our reflection is.
Why can't you tickle yourself?
Your brain predicts the touch of your own movement and tones it down. A surprise touch from someone else is what makes it tickle.
If yesterday were tomorrow, today would be Friday. What day is it today?
Sunday. Yesterday is Saturday, and Saturday is the day after Friday.
Can you answer the question 'Will your next word be no?' truthfully with a yes or no?
No. If you say no, your word was no, so the truth is yes. If you say yes, the answer should have been no.
Why are manhole covers round?
A round cover cannot fall through its own hole, because its width is the same in every direction.
Why does ice float on water?
Water expands as it freezes, so ice is less dense than liquid water and sits on top.
Why is it colder at the top of a high mountain, even though it is closer to the Sun?
The thinner air holds less heat, and the Sun's distance changes by a tiny amount compared with the whole way to the Sun.
Hard Riddles That Make You Think
A map of a country is laid flat on the ground inside that country. Must some point of the map lie exactly over the place it shows?
Yes. A continuous map of a region into itself always leaves one point fixed, which is a result known as Brouwer's fixed point theorem.
At any party with two or more guests, must two people have shaken the same number of hands?
Yes. With n guests the counts run from 0 to n - 1, but 0 and n - 1 cannot both occur, so only n - 1 values are possible for n people.
Assuming temperature changes smoothly, are there always two opposite points on Earth with exactly the same temperature?
Yes. Go round any circle that splits the globe in half. The temperature difference between opposite points swings from positive to negative, so it is zero somewhere.
Aristotle said heavy things fall faster than light ones. Galileo tied a heavy ball to a light one and dropped them together. What contradiction does he find?
The light ball should slow the heavy one, so the pair falls slower than the heavy ball. But together they are heavier, so they should fall faster. Both cannot be true.
Achilles runs at 10 metres per second and a tortoise crawls at 1 metre per second, with a 100 metre head start. When does Achilles catch it?
After 100/9, about 11.1 seconds. He gains 9 metres each second, so the 100 metre gap closes in that time.
You drive the first mile of a two mile trip at 30 miles per hour. How fast must you drive the second mile to average 60 miles per hour overall?
No speed is enough. Averaging 60 over 2 miles needs 2 minutes in total, and the first mile already took 2 minutes.
If the Sun suddenly vanished, about how long would it take before we saw the sky go dark?
About eight minutes, which is how long sunlight takes to reach Earth.
In the northern hemisphere, is the Earth closer to the Sun in summer or in winter?
In winter. Earth is nearest the Sun in early January. The seasons come from the tilt of the Earth, not its distance.
How many colours are always enough to colour any flat map so that no two bordering regions match?
Four, a result known as the four colour theorem.
How far can you walk into a forest?
Halfway. After that point you are walking out of it.
Quick-Fire Riddles That Make You Think
Is a light-year a measure of time or of distance?
Distance.
What is lost the moment you boast about having it?
Humility.
What is always ahead of you and can never be reached?
The horizon.
What can you never take back once it has been spoken?
Words.
What is easy to make and hard to keep?
A promise.
What gets heavier the longer you carry it, even though it weighs nothing?
A grudge.
What does a candle lose when it lights another candle?
Nothing.
What can a closed mind never do?
Learn.
How to Think Through These Riddles
These riddles reward slow thinking. For the idea riddles, picture the thing and ask what it does and what it never does. For the thought experiments, state the question in your own words, decide what each word means, and notice where the usual answer breaks. The sound in the forest is a good example of a question that changes with the meaning of a single word.
Talk them through with a friend. Disagreement is useful, because each person has to say why. When you read an answer, ask whether you accept the reasoning, not just the conclusion. If you can explain the trick to someone else, you have understood the riddle rather than only memorised it.
Frequently Asked Questions
What kind of riddles make you think?
Riddles about ideas, paradoxes and thought experiments make you think, because the answer depends on reasoning rather than a quick guess. Everyday puzzles about sound, maps and speed are good examples.
Are these riddles good for discussion groups?
Yes. Many have more than one reasonable view, such as the falling tree and the ship of planks. Read one aloud, let people argue it, and then share the explanation.
Do all of these riddles have one right answer?
The idea riddles and the hard set have definite answers. A few in the trickier set, such as the tree and the ship, have an answer that depends on how you define a word, and the explanation says so.
How can I use these riddles to sharpen my thinking?
Try to explain each answer in one sentence without reading it first. Then compare your reasoning with the explanation, and note where you assumed something that was not stated.
