Logic puzzles and brain teasers
Train reasoning with classic and modern logic problems — by difficulty, with hints and full solutions.
All puzzles
Farmer, Fox, Chicken, and Grain
EasyA farmer must cross a river with a fox, a chicken, and grain. How can he do it without losing anything?
Three Switches and One Light Bulb
MediumThree switches control one bulb in another room. Can you identify the right switch with only one visit?
Blue-Eyed Islanders
HardEveryone can see others’ eye colors, but not their own. One public statement changes everything.
Burning Ropes Timer
HardTwo ropes each burn for 60 minutes, but not at a uniform rate. Can you measure exactly 45 minutes?
Prisoners and Hats
HardA line of prisoners must guess their hat colors. Can they use strategy to save as many people as possible?
Three Gods Riddle
HardThree gods are named True, False, and Random. Can you identify each of them using only three yes-or-no questions?
Monty Hall Problem
HardYou choose 1 of 3 doors. The host opens a goat door. Should you switch or stay?
Counterfeit Coin Puzzle
HardOne of 12 coins is counterfeit and may be heavier or lighter. Can you find it in just 3 weighings?
Poisoned Wine Bottles
HardYou have 1000 wine bottles, one is poisoned, and 10 test subjects. Can you find the poisoned bottle in one round?
Bridge and Torch Problem
HardFour people must cross a bridge at night with one torch. Can you find the fastest way?
Mislabeled Boxes
MediumThree boxes are labeled “Apples,” “Oranges,” and “Apples & Oranges,” but every label is wrong. Can you relabel them with...
Lily Pad Growth
EasyLily pads double every day. If the pond is full on day 48, on what day is it half full?