Logic puzzles and brain teasers
Train reasoning with classic and modern logic problems — by difficulty, with hints and full solutions.
All puzzles
100 Doors Problem
MediumAfter toggling 100 doors in a pattern, which doors remain open at the end?
Airplane Seat Paradox
MediumThe first passenger sits randomly. What is the chance the last passenger gets their own seat?
25 Horses and the Fastest 3
MediumYou can race only 5 horses at a time and have no stopwatch. How many races are needed to find the fastest 3?
Two Eggs and 100 Floors
MediumWith only 2 eggs, what is the minimum number of drops needed to guarantee finding the critical floor?
Poisoned Chocolate Bars
MediumOne of 8 chocolate bars is poisoned. With only 2 testers, can you identify it in one round?
Three Switches and One Light Bulb
MediumThree switches control one bulb in another room. Can you identify the right switch with only one visit?
Mislabeled Boxes
MediumThree boxes are labeled “Apples,” “Oranges,” and “Apples & Oranges,” but every label is wrong. Can you relabel them with...
Three Switches and One Light Bulb
MediumThree switches control one light bulb in another room. Can you identify which switch controls it with only one visit?