From an interview$^\color{red}{\star}$ with Vladimir Arnol'd:
Lui: Please tell us a little bit about your early education. Were you already interested in mathematics as a child?
Arnol′d: The Russian mathematical tradition goes back to the old merchant problems. Very young children start thinking about such problems even before they have any knowledge of numbers. Children five to six years old like them very much and are able to solve them, but they may be too difficult for university graduates, who are spoiled by formal mathematical training. A typical example is:
You take a spoon of wine from a barrel of wine, and you put it into your cup of tea. Then you return a spoon of the (nonuniform!) mixture of tea from your cup to the barrel. Now you have some foreign substance (wine) in the cup and some foreign substance (tea) in the barrel. Which is larger: the quantity of wine in the cup or the quantity of tea in the barrel at the end of your manipulations?
Does anybody know where I can find more of these old merchant problems?
$\color{red}{\star}\quad$ S. H. Lui, An interview with Vladimir Arnol′d, Notices of the AMS, April 1997.
