1 km2 = 100 hectare, 1 hectare = 100 hectare, 1 hectare = 100 square meter. 1 m2 = 100 square decimeter. 1 square decimeter = 100 square centimeter, 1 square kilometer = 100000 square meter.

The conversion of primary school area units is introduced as follows:

Unit conversion is one of the key points in primary school mathematics learning. Calculation, filling in the blanks, selection and application will all involve unit conversion. If the child's memory of unit conversion is not deep enough, it will always be confused and the test score will be pulled down.

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. Frieden Noel, a Dutch educator, said: "Mathematics comes from reality and must be rooted in reality and applied to reality."

Indeed, modern mathematics requires us to observe the world from a mathematical perspective and explain the world in mathematical language. Judging from the mathematics learning psychology of primary school students, the learning process of students is not a passive absorption process, but a reconstruction process based on existing knowledge and experience.

Therefore, learning while doing and learning while playing will make children learn more actively. From our educational goal, while imparting knowledge, we should pay more attention to cultivating students' comprehensive ability of observation, analysis and application.

In primary school mathematics education, we should pay attention to cultivating students' mathematical thinking and creative thinking, encourage students to find and ask questions, and cultivate students' interest and spirit in mathematics through classroom inquiry and practical activities. At the same time, primary school mathematics has laid a solid foundation for further study and helped students better cope with their future study and life.

Number and algebra, number and algebra mainly include reading and writing methods of numbers (integers, decimals, fractions), rewriting of numbers (turning them into numbers in tens of thousands and hundreds of millions, seeking divisors, etc. ) and compare the sizes of numbers (integers, decimals, fractions).