A certain stock exchange designates each stock with a one-, or two-, or three-letter code, where each letter is selected from the 26 letters of the alphabet. If the letters may be repeated and if the same letters used in a different order constitutes a different code, how many different stocks is it possibly to uniquely designate with these codes?
京公网安备11010202008513号 京ICP证101109号 京ICP备12012021号
发表于 2007-9-6 18:22:00
