// logic-puzzles
Classic logic puzzles that challenge your reasoning abilities and creative thinking.
1 min read The 25 horses puzzle asks for the 3 fastest horses using 5-horse races and no timer. The answer is 7 races — here’s the reasoning, why 6 isn’t enough, and the variations. Read article
5 min read The 100 Doors Puzzle: Parity, Perfect Squares, and Why Divisor Counts Matter The 100 doors puzzle is a beautiful number-theory Read article
5 min read The Bridge Crossing Puzzle: Four People, One Flashlight, 17 Minutes The bridge-crossing puzzle is a classic interview question that appears Read article
5 min read Find the Counterfeit Coin: 10 Coins (or N Coins), One Different, Minimum Weighings Counterfeit coin puzzles are a classic interview Read article
1 min read How can you get a fair coin toss if someone hands you a coin that is weighted to come up Read article
3 min read Problem: you have 100 doors in a row that are all initially closed. you make 100 passes by the doors Read article
4 min read Problem: you have two jars, 50 red marbles, 50 blue marbles. you need to place all the marbles into the Read article
3 min read problem: two trains enter a tunnel 200 miles long (yeah, its a big tunnel) travelling at 100 mph at the Read article
3 min read Two MIT math grads bump into each other at Fairway on the upper west side. They haven’t seen each other Read article
3 min read Problem: this year on October 2, 2001, the date in MMDDYYYY format will be a palindrome (same forwards as backwards).10/02/2001when Read article
4 min read Problem: you are given a sequence of numbers from 1 to n-1 with one of the numbers repeating only once. Read article
6 min read Five pirates have 100 gold coins. they have to divide up the loot. in order of seniority (suppose pirate 5 Read article
5 min read 100 fogcreek programmers are lined up in a row by an assassin. the assassin puts red and blue hats on them. Read article
3 min read A bad king has a cellar of 1000 bottles of delightful and very expensive wine. A neighbouring queen plots to Read article
3 min read Problem: this one is a classic that many of you have probably already heard, but all the more reason why Read article
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