Brain Teasers
This is our general mix: short puzzles with exactly one right answer, drawn from number problems, letter sequences, logic lineups and questions with a catch. A notebook and a pen that cost a dollar ten, four cards making claims about each other, a digital clock showing 11:11. Each fits in a few lines and can be solved in your head or on a napkin.
A good brain teaser feels unfair for about a minute and obvious once you see it. The answer should follow from what the puzzle says, with no hidden assumptions and no second answer a clever solver could defend. After the reveal, every card shows the working, so you can see where your thinking went sideways. For more of one kind, try the rebus puzzles, the lateral thinking puzzles or the tricky questions.
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01 · MediumClassic
A notebook and a pen cost $1.10 together. The notebook costs exactly $1.00 more than the pen. How much does the pen cost?
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02 · Easy
What number comes next: 2, 6, 12, 20, 30, ?
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03 · Hard
Four cards lie face up. Card A says: "Exactly one of these four cards is true." Card B says: "Exactly two are true." Card C says: "Exactly three are true." Card D says: "All four cards are false." Which card is true?
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04 · Medium
Which letter comes next: B, D, G, K, P, ?
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05 · Medium
What number comes next? 2, 3, 5, 9, 17, 33, ...
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06 · Medium
Which is more: a dozen dozen, or half a gross?
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07 · Medium
Cara is at the front of a line of four friends. Dev stands directly behind Ava. Ben is not at either end of the line. Who is at the back?
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08 · HardClassic
How many squares of any size can you find on a standard 8 by 8 chessboard?
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09 · Medium
A 24-hour digital clock runs from 00:00 to 23:59. It now shows 11:11. How many minutes until it next shows four identical digits?
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10 · Easy
What letter comes next? Z, X, V, T, R, ...
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11 · Easy
I'm a whole number between 20 and 30. I'm one less than a multiple of 5 and one more than a multiple of 7. What number am I?
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12 · Easy
Which single word can go in front of "fly", "cup" and "milk" to make three new words?
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13 · Medium
What number comes next? 31, 28, 31, 30, 31, ...
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14 · MediumClassic
If 5 machines take exactly 5 minutes to make 5 widgets, how many minutes would 100 of the same machines take to make 100 widgets?
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15 · MediumClassic
What letter comes next? O, T, T, F, F, S, S, E, ...
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16 · Easy
I'm a four-digit number. Reading from left to right, each digit is exactly one more than the digit to its right, and all my digits add up to 10. What number am I?
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17 · MediumClassic
If you write out every whole number from 1 to 100, how many times do you write the digit 9?
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18 · Medium
What number comes next? 3, 6, 11, 18, 27, ...
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19 · Medium
In 2 years Zara will be exactly twice as old as she was 5 years ago. How old is Zara now?
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20 · Medium
A rectangle has whole-number side lengths in centimeters. Its perimeter is 20 cm and its area is 21 square cm. How long are its sides?
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21 · HardClassic
Three books, volumes 1, 2 and 3, stand in order from left to right on a shelf, spines facing you, as books normally stand. Each volume's pages are 4 cm thick and each cover is 0.5 cm thick. A bookworm chews in a straight line from the first page of volume 1 to the last page of volume 3. How far does it chew?
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22 · EasyClassic
A drawer holds 6 black socks and 6 white socks, all mixed up. In the dark, how many socks must you take out to be certain of having a matching pair?
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23 · Easy
A grocer stacks oranges in a square pyramid with 4 layers. The top layer is 1 orange, the next is a 2 by 2 square, then 3 by 3, and the bottom is 4 by 4. How many oranges are in the stack?
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24 · Easy
You face north. You turn 90 degrees to your right three times, then turn 180 degrees to your left. Which direction are you facing now?
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25 · Medium
In a non-leap year, what is the date exactly 100 days after 1 January?
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26 · Easy
What number comes next? 1, 8, 27, 64, ...
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27 · Easy
You fold a sheet of paper exactly in half, then in half again, and so on. How many folds does it take to make exactly 32 layers?
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28 · Easy
Which is bigger: the number of seconds in one hour, or the number of minutes in 60 hours?
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29 · Medium
A noughts-and-crosses board is a 3 by 3 grid of small squares. Counting squares of every size whose sides lie on the grid lines, how many squares are there?
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30 · Medium
What number comes next? 1, 2, 6, 24, 120, ...
How to use brain teasers with a group
Read a teaser aloud, then wait in silence for a full minute before taking answers; the first answer shouted out is often the tempting wrong one, and the pause gives careful solvers their chance. Ask whoever gets it right to explain the working before you reveal the card. Teasers make a good opener for a meeting or a class, with one puzzle at the start and the answer at the end, and they travel well on a road trip if the reader keeps the answers private.
Tips for solving brain teasers
- Write the numbers down; teasers like the notebook and pen are built so the answer your head jumps to is wrong.
- For sequences, check the gaps between terms first, then whether each term doubles or follows a rule from the one before.
- In logic lineups, sketch the positions as blank boxes and fill in the fixed clues before the relative ones.
- Use the difficulty filter to start with easy teasers if the group is new to them, then work up.
How this page was checked
Every riddle here went to a second solver without its answer. When they reached a different answer that also fit, the riddle was rewritten and tested again, or cut. Our editorial standards.
- Drafted for this page
- 42
- Solved blind
- 30
- Cut as repeats of other pages
- 10
- Original to this site
- 23