Age of the captain
The age of the captain is a mathematical word problem which cannot be answered even though there seems to be plenty of information supplied. It was given for the first time by Gustave Flaubert in a letter to his sister Caroline in 1841: Puisque tu fais de la géométrie et de la trigonométrie, je vais te donner un problème : Un navire est en mer, il est parti de Boston chargé de coton, il jauge 200 tonneaux. Il fait voile vers le Havre, le grand mât est cassé, il y a un mousse sur le gaillard  d’avant, les passagers sont au nombre de douze, le vent souffle N.-E.-E., l’horloge marque 3 heures un quart d’après-midi, on est au mois de mai…. On demande l’âge du capitaine? Since you are now studying geometry and trigonometry, I will give you a problem. A ship sails the ocean. It left Boston with a cargo of wool. It grosses 200 tons. It is bound for Le Havre. The mainmast is broken, the cabin boy is on deck, there are 12 passengers aboard, the wind is blowing East-North-East, the clock points to a quarter past three in the  afternoon. It is the month of May. How old is the captain? More recently, a simpler version has been used to study how students react to word problems: A captain owns 26 sheep and 10 goats. How old is the captain? Many children in elementary school, from different parts of the world, attempt to "solve" this nonsensical problem by giving the answer 36, obtained by adding the numbers 26 and 10. It has been suggested that this indicates schooling and education fail to instill critical thinking in children, and do not teach them that a question may be unsolvable. But , others have countered that in education students are taught that all questions have a solution and that giving any answer is better than leaving it blank, hence the attempt to "solve" it.