It takes 20 classes to finish. The second volume of the second grade mathematics textbook of Jiangsu Education Press includes the following contents: the transformation of graphics, the understanding of cuboids and cubes, the meaning and nature of fractions, the addition and subtraction of fractions, statistics, the wide angle and comprehensive application of mathematics, etc. Among them, factors and multiples, cuboids and cubes, the meaning and nature of fractions, addition and subtraction of fractions, statistics and so on are the key contents of this textbook.