World’s Most Challenging Puzzles

To solve the world’s most challenging puzzles, sometimes you have to be smart, sometimes patient, and sometimes you just have to pay attention. Try these: if you can bicycle 1 km in four minutes against the wind, and cycle 1 km in three minutes with the wind, how long will it take you to bicycle 1 km without any wind?; Arrange seven pieces of chalk so that each one is touching all the others.; If you have one pipe, an oil lamp, and a wood-burning stove, and only one match, which item would you light first? These and other devilishly tricky problems dare you to match wits with the greatest puzzlers of all time. Take on all 95 of these stumpers yourself and then challenge your friends.