Guess the Playing Cards
There are three playing cards in a row. There is a heart to the left of a diamond. There is a five to the right of a jack. There is a club to the left of a diamond. There is…
Chain Links Puzzle
You have 5 short chains of 3 links each, that you would like to connect into one long 15-link chain. To connect links, you need to cut open a link, join it with another link, and then close it. What…
Bishop Holds Back the Pawns
A pretty challenging chess puzzle, because there isn’t a pre-determined number of moves. White to play and force a draw.
Odd One Out
Which is the odd one out? catwoman deus ex machina parishioner pyromania scuba
24 Game Puzzle
How do you use 3, 3, 8, and 8 to make 24? Each number must be used exactly once, and only addition, subtraction, multiplication, division, and parentheses can be used.
Math Rebus
What math-related word/phrase does this rebus represent?
5 Pirates Puzzle
Five pirates are figuring out how to divide up a newly plundered treasure of 100 gold coins. From most senior to least senior: Pirate A, Pirate B, Pirate C, Pirate D, and Pirate E. The rules: The most senior pirate…
Bishop Wins the Day
White to play and mate in two moves.
Match Maximization
What is the biggest number you can make by moving exactly 2 matches in the number above? Assume that numbers must be represented in their standard “digital clock” font (for example, a “1” requires two segments).
A and B
A + B = A * B = A / B What are the values of A and B?
Wrong Seat Probability
There is a fully-booked flight with 100 seats. The first person decides to ignore the seat assignments, and sits in a random seat. Each subsequent person sits in their assigned seats if available, or sits in a random unoccupied seat…
Solitary Word
I am a solitary word. If I lose my first letter, I remain the same. If I lose my first letter again, I still remain the same. What am I?
Sword is Mightier than the Bow
Shot two arrows at its center and missed both times,swung a sword once at its center and hit twice.What is it?
Swap Digits
Swap two of the digits in this equation to make it a valid equation: 7 x 7 + 9 x 9 = 138
Card Pairing Game
You are playing a game with your friend using a standard deck of 52 playing cards. Each round, you flip over two cards: If both cards are black, you keep the cards and earn one point. If both cards are…
Square in a Square
In the larger square, there is a smaller square formed by lines connecting each corner to the midpoint of one of the sides. Question: What fraction of the larger square is the smaller filled square?
Base Rate Fallacy
What is the Base Rate Fallacy? In simple terms, it’s a common error we make in assessing likelihoods due to (a) over-emphasizing the rate of something within a group and (b) under-emphasizing how common that group is in the first…
Rebus Puzzle 1
What common word or phrase is this rebus referring to?
Nob’s Number Tree Puzzle
Nob’s Number Tree What number belongs in the “?” circle? Note that all numbers shown are correct, there are no typos or errors. Nob Yoshigahara’s Puzzles Nob’s Number Tree is a well-known brainteaser by the Japanese puzzle guru Nobuyuki “Nob”…
Missing Dollar Riddle
The missing dollar riddle is a classic brain teaser that can trip up even savvy puzzle solvers: Three friends split the cost of a hotel room. They are charged $30, so each of them pays $10. Later the hotel manager…
Divisible by 100
Prove that for any set of one hundred whole numbers, either one of those numbers is divisible by 100 or the sum of a subset of those numbers is divisible by 100.
Throwing a Ball
When you throw a ball straight up, does it spend more time going up, more time coming down, or the same time going up and down – taking into account both gravity and air resistance?
Chance of Rain
You are driving to Seattle to meet some friends, and want to know whether you should bring an umbrella. You call up 3 of your friends who live there and independently ask them if it’s raining. Your friends like to…
Seven Times the Sum of Its Digits
Which two-digit numbers are exactly equal to seven times the sum of its digits?
Pigeonhole Principle
The Pigeonhole Principle is a simple and elegant concept: If you place more than n pigeons into n pigeonholes, at least one of the pigeonholes must contain more than one pigeon. More generally, if you need to make more than…