Hebei Education Publishing House Elementary School Mathematics "Combination and Division" Lesson 10. Primary school mathematics is to teach children a series of knowledge about number, four operations, the calculation formula of figure and length, unit conversion and so on through textbooks, which lays a good mathematical foundation for junior high school and daily life calculation. Hebei Education Press, the first volume of the first grade of mathematics, 10: Solving the problem of division and combination by the method of transformation.