Wolf, goat, and cabbage
A farmer must ferry a wolf, a goat, and a cabbage across a river. The boat holds the farmer plus at most one item. The w…
SolutionOpen puzzle: Wolf, goat, and cabbage
Puzzle bank
Logic and brain teasers as cards; tap to reveal answers when available.
21 puzzles
Heaven and hell: two doors
Two doors: one leads to heaven, one to hell. Each door has a guard—one always tells the truth, one always lies (you do n…
SolutionOpen puzzle: Heaven and hell: two doorsCounting game (21)
Two players take turns counting upward from 1. On each turn you may add 1, 2, or 3 to the current number (so you say the…
SolutionOpen puzzle: Counting game (21)Monty Hall problem
You face three doors: one hides a car, the other two each hide a goat. Pick the door with the car and you win.
SolutionOpen puzzle: Monty Hall problemDrunk passenger boarding
A plane has 100 seats labeled 1 through 100. One hundred passengers board in order.
SolutionOpen puzzle: Drunk passenger boardingBlindfold coin partition
A pile of n coins lies on a table, some heads up and some tails up. You are blindfolded but may touch and move coins.
SolutionOpen puzzle: Blindfold coin partitionTwo uneven burning ropes
You have two ropes that each burn for exactly one hour when lit from one end, but they burn non-uniformly along their le…
SolutionOpen puzzle: Two uneven burning ropesNim
Several piles of tokens. Players alternate taking at least one token from a single pile. The player who takes the last t…
SolutionOpen puzzle: NimBlack and white hats
A group plays a game: each person gets a white or black hat at random (at least one black hat). Everyone sees others’ ha…
SolutionOpen puzzle: Black and white hatsThree prisoners in a line
Three prisoners stand in a row: front, middle, back. The person at the back sees both hats ahead; the middle person sees…
SolutionOpen puzzle: Three prisoners in a lineThree hat guessers
Three people each wear a hat colored red, yellow, or blue (repeats allowed, e.g. YYB, RYB, RRR…). Each person sees only …
SolutionOpen puzzle: Three hat guessersFour glasses on a rotating table
There is a square table whose top can rotate. A glass is placed at each corner.
SolutionOpen puzzle: Four glasses on a rotating tableFive pirates and 100 gold coins
Five rational pirates—A, B, C, D, and E—find 100 gold coins to split.
SolutionOpen puzzle: Five pirates and 100 gold coinsTwelve balls on a balance
You have 12 identical-looking balls. Eleven weigh the same; one is either heavier or lighter than the rest, and you do n…
SolutionOpen puzzle: Twelve balls on a balanceCheryl's birthday
Albert and Bernard just met Cheryl and want to know her birthday. Cheryl gives ten possible dates:
SolutionOpen puzzle: Cheryl's birthdayPoison and lab mice
There are 1000 bottles of liquid and exactly one contains poison that kills one hour after drinking. The poison can be d…
SolutionOpen puzzle: Poison and lab miceBlue and red eyes
Rule: Anyone who knows their own eye color must commit suicide at noon the next day.
SolutionOpen puzzle: Blue and red eyes100 prisoners and boxes
100 prisoners numbered 1–100. In a room are 100 closed drawers, each containing one number, forming a random permutation…
SolutionOpen puzzle: 100 prisoners and boxesEinstein's five houses
Five houses in a row, each a different color. Each house has a different nationality, pet, drink, and cigarette brand. C…
SolutionOpen puzzle: Einstein's five houses100 prisoners and a lamp
A prison holds 100 inmates, each in a sealed cell with no way to meet or communicate. They follow a regular daily routin…
SolutionOpen puzzle: 100 prisoners and a lampThe hardest logic puzzle ever
Three gods are labeled A, B, and C. You know their types are Truth, Lie, and Random, but not which label has which type.
SolutionOpen puzzle: The hardest logic puzzle ever