http://io9.com/the-answer-to-this-puzzle-is-not-what-youd-expect-1701881343
An airplane flies in a straight line from airport A to airport B, then back in a straight line from B to A. It travels with a constant engine speed and there is no wind. Will its travel time for the same round trip be greater, less, or the same if, throughout both flights, at the same engine speed, a constant wind blows from A to B?
Answer here:
http://io9.com/how-quickly-can-you-cross-this-bridge-1703447829
