请问：用2.3.4.5.6组成的二位数乘以三位数有几个

your question a little bit blur...
anyway i try to solve for you from what i understand:

there are 5P2 = 20 combinations of 2 digits number formed by these 5 numbers.

there are 5P3 = 60 combinations of 3 digits number formed by these 5 numbers.

your question ask for 20 x 60 = 1200.

if that is not what you mean please further explain ya...

ps: sorry because my comp cant write in Chinese... ;p