37 puzzles with answers · tap one to see its answer
Hard Brain Teasers and Riddles
These 37 hard brain teasers and riddles take more than one step: a clue to combine with another, a riddle whose every line has to fit or a puzzle that looks impossible until you see it from the side. Each has one airtight answer and an explanation. Take your time, and use paper: most are easier written down.
Every puzzle was solved by a second reader who had not seen the answer, on November 9, 2026.
A builder puts up a square cabin with one window in each of its four walls, and every one of the four windows faces south. Where is the cabin?
Answer: At the North Pole
Why: At the North Pole every direction is south, so each wall faces south whichever way it is turned.
I have thirteen hearts, but none of them beat. I have four kings who rule nothing and four queens who wear no real crowns. What am I?
Answer: A deck of playing cards
Why: A standard deck has 13 cards in each suit, including hearts, and a king and a queen in each of its four suits.
My roots reach deeper than any tree's, I stand far taller than any tree, and yet no one has ever watched me grow. What am I?
Answer: A mountain
Why: A mountain's base runs deep into the Earth and its peak towers over every tree, but it grows far too slowly for anyone to see.
You can spend me, waste me, save me and lose track of me, but you can never stop me, and every clock keeps count of me. What am I?
Answer: Time
Why: We spend, waste and save time and lose track of it, and clocks measure it as it passes without ever stopping.
You are standing in a field, facing north. You turn right, then turn to face the opposite way, then turn left, and then turn left once more. Which way are you facing now?
Answer: East
Why: Turning right takes you from north to east, facing the opposite way takes you to west, the first left takes you to south, and the second left brings you back to east.
I'm made of water, yet I float high over the hills. When I grow dark and heavy, everyone below reaches for an umbrella, and my shadow drifts across the fields as I pass. What am I?
Answer: A cloud
Why: A cloud is a mass of tiny water drops floating in the sky. When it gets heavy, it rains, and it casts a moving shadow on the ground beneath it.
In which book does Friday come before Monday, Saturday come before Wednesday, and today come before yesterday?
Answer: A dictionary
Why: A dictionary lists words in alphabetical order, and F comes before M, S before W, and t before y.
Today is a Sunday. What day of the week will it be 100 days from today?
Answer: Tuesday
Why: 100 days is 14 full weeks (98 days) plus 2 days. After 14 weeks it is Sunday again, and 2 more days makes it Tuesday.
I fill every room the moment the last lamp goes out. I hide under beds and in the backs of closets, and one small match chases me away. What am I?
Answer: Darkness
Why: When the lights go off, darkness fills the room and lingers in hidden corners until any light appears.
Yesterday, I was called tomorrow. Tomorrow, I'll be called yesterday. What am I?
Answer: Today
Why: Seen from yesterday, today was 'tomorrow', and seen from tomorrow, today will be 'yesterday'.
Out of the bag I'm black as a crow, under the grill I glow red-hot for hours, and by the end of the cookout I'm a heap of soft gray powder. What am I?
Answer: Charcoal (or coal)
Why: Charcoal is black in the bag, glows red-hot as it burns under the grill, and ends up as gray ash.
I build castles that the tide knocks down, I sting your eyes on a windy beach, and I'm made from rock ground down by wind and waves over ages. What am I?
Answer: Sand
Why: Sand is rock worn into tiny grains by wind and water over a very long time. It makes sandcastles and blows into your eyes at the beach.
I answer every shout across a canyon, but only with the words you gave me, and always a moment late. What am I?
Answer: An echo
Why: An echo is your own voice bouncing back off a distant surface, so it repeats you after a short delay.
I have rings but no fingers, I'm a giant who never stomps, and I'm sixth in line from the Sun. What am I?
Answer: Saturn
Why: Saturn is a giant planet, the sixth from the Sun, and it is famous for its wide rings.
A train 1 kilometer long travels at a steady 1 kilometer per minute into a tunnel that is also 1 kilometer long. How long is it from the moment the front of the train enters the tunnel until the very back of it comes out?
Answer: 2 minutes
Why: The front has to travel the tunnel's 1 kilometer plus the train's own 1 kilometer before the back clears the exit: 2 kilometers at 1 kilometer per minute.
At dawn it creeps on four, by midday it strides on two, and in its evening it leans on three. What is it?
Answer: A person, over a lifetime
Why: A baby crawls on hands and knees, an adult walks on two legs, and many older people walk with a cane. Dawn, midday and evening stand for the stages of a life.
Two curved rows of white guards stand on pink hills. All day they chomp and grind, and at night they rest in the dark, waiting for breakfast. What are they?
Answer: Teeth
Why: Your teeth sit in two curved rows on your pink gums, and they bite and chew your food all day long.
A plane takes off at 9:00 a.m., flies for exactly 3 hours, and lands at 9:00 a.m. local time. Every clock involved is correct. How?
Answer: It flew west across three time zones
Why: Each time zone to the west sets its clocks an hour earlier, so crossing three of them cancels out the 3 hours of flying on the local clock.
When Rosa was 8, her little brother was half her age. Rosa is 71 now. How old is her brother?
Answer: 67
Why: Half of 8 is 4, so her brother is 4 years younger than Rosa, and he always will be. 71 - 4 = 67, not half of 71.
Two days ago, Mia was 30. Next year, she will turn 33. What is today's date, and when is Mia's birthday?
Answer: Today is January 1; her birthday is December 31
Why: On December 30 she was 30, and on December 31 she turned 31. She turns 32 at the end of this year and 33 at the end of next year.
Nobody ever buttons me up or hangs me in a closet, yet I'm a coat, and I'm always wet on the day I go on. What kind of coat am I?
Answer: A coat of paint (or varnish)
Why: A fresh coat of paint goes on wet and dries afterward, and it is walls and fences that wear it, not people.
Comedians crack me, pranksters play me on April Fools' Day, and at every family dinner someone tells me. What am I?
Answer: A joke
Why: People crack jokes, play jokes on each other and tell jokes, and no other common thing fits all three.
Miners dig me out of the ground, then I'm glued inside a thin stick of wood that I never get out of, and yet nearly everyone has used me at school. What am I?
Answer: Pencil lead (graphite)
Why: The 'lead' in a pencil is graphite, a mined mineral that is sealed inside the pencil's wooden casing for good.
Dinosaurs saw me, and so did the very first fish, yet my age starts over at 'new' every month, so I'm never much more than a month old. What am I?
Answer: The Moon
Why: The Moon itself is billions of years old, but its cycle of phases starts over with a new moon about every 29.5 days.
Three switches in a hallway are all off. One of them controls an old-fashioned incandescent bulb in a closed attic, and the other two do nothing. You may flip the switches as often as you like, but you may go up to the attic only once. How can you tell which switch works the bulb?
Answer: Leave switch 1 on for a while, turn it off, turn on switch 2, then go look
Why: If the bulb is lit, it's switch 2. If it's dark but warm to the touch, it's switch 1, which heated it up. If it's dark and cold, it's switch 3.
You see a wall clock in a mirror. Its face has no numbers, and its hands appear to show 4:20. What time is it really?
Answer: 7:40
Why: A mirror flips the clock face left to right, so the real time and the time it appears to show always add up to 12:00. 12:00 - 4:20 = 7:40.
A rope ladder hangs over the side of a boat floating in a harbor, with its bottom 3 rungs under water. Over the next few hours, the tide rises by 1.5 meters. How many rungs are under water now?
Answer: Still 3
Why: The boat floats, so it rises with the tide, and the ladder hanging from it rises by exactly the same amount.
You have two coins worth 15 cents in total, and one of them is not a 5-cent coin. The only coins in use are 1-cent, 5-cent, 10-cent and 25-cent coins. What are your two coins?
Answer: A 10-cent coin and a 5-cent coin
Why: Only a 10 and a 5 make 15 cents with two coins. The 10-cent coin is the one that is not a 5-cent coin; the other one is.
Zara bets her brother she can lay an ordinary pencil on the bedroom floor, in plain sight and with nothing on top of it, so that he can't jump over it. Where does she put it?
Answer: Flat against the bottom of a wall (or in a corner)
Why: With the pencil pressed against a wall, there is no far side to land on, so no one can jump over it.
Lay me on my side and I go on forever. Cut me in half across my middle and I'm nothing at all. What am I?
Answer: The number 8
Why: An 8 lying on its side looks like the infinity sign, and slicing it across the middle leaves two zeros.
A courier only accepts boxes whose sides are all 1.2 meters long or less. Mo needs to send a fishing rod that is 1.5 meters long and can't be bent or taken apart. How can he send it?
Answer: Lay it diagonally across a box, such as one 1.2 m by 1.2 m
Why: No side of a 1.2 m by 1.2 m box is too long, but its corner-to-corner diagonal is about 1.7 m (1.2 x 1.2 + 1.2 x 1.2 = 2.88, and 1.7 x 1.7 = 2.89), so the 1.5 m rod fits with room to spare.
One of us breaks every morning but never falls. The other falls every evening but never breaks. What are we?
Answer: Day and night
Why: Day breaks at dawn (daybreak) and night falls at dusk (nightfall), every single day.
When does 8 plus 8 equal 4, and 10 plus 5 equal 3?
Answer: When you add hours on a 12-hour clock
Why: 8 hours after 8 o'clock it is 4 o'clock, and 5 hours after 10 o'clock it is 3 o'clock.
Two English books stand side by side on a shelf in the usual way, spines facing you: Volume 1 on the left, Volume 2 on the right. Each book's pages are 3 cm thick in total, and each cover is 2 mm thick. A bookworm chews in a straight line from page 1 of Volume 1 to the last page of Volume 2. How far does it travel?
Answer: 4 mm
Why: With the spines facing you, page 1 of Volume 1 sits at that book's right side, against Volume 2, whose last page sits at its left side. So the worm goes through just two covers: 2 + 2 = 4 mm.
Leo points to a woman and says, 'Her mother is my mother's mother-in-law.' Leo's parents are married to each other. How is the woman related to Leo?
Answer: She is his aunt (his father's sister)
Why: Leo's mother's mother-in-law is his father's mother, Leo's grandmother. So the woman is a daughter of Leo's paternal grandmother: his father's sister, Leo's aunt.
Rhea lived long ago. She was 30 years old in the year 1990 and 35 years old in the year 1985, and both facts are true. How?
Answer: The years were BCE (BC), which count down toward year 1
Why: BCE years count backward, so 1985 BCE came five years after 1990 BCE. Rhea was born in 2020 BCE.
How can you cut a round cake into 8 equal pieces with just 3 straight cuts, without moving or stacking any of the pieces?
Answer: Two cuts in a cross from above, then one cut sideways through the middle
Why: Two cuts at right angles through the center make 4 equal wedges. One horizontal cut halfway up the cake splits every wedge in two, giving 8 equal pieces.