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 1km in four minutes against the wind, and cycle 1km in three minutes with the wind, how long will it take you to bicycle 1km without any wind?
• Arrange seven pieces of chalk so each one is touching all the others.
• If you have a pipe, an oil lamp, and a wood-burning stove, and only match, which item would you light first?