Hectares and square kilometers are two large-area units, which are beyond the scope of students' visual perception and difficult to master. We can help students form a good sense of quantity by the following methods.

Square meter (square m2 in English) is the metric unit of area, which is defined as the area of a square with a side length of 1 meter. In life, the square meter is usually called "square meter" or "square meter", and it is called "square meter" in Hongkong and Taiwan Province. Square meter is an international unit of area and a commonly used measurement standard in life and work.

The definition is that the area of a square with a side length of 1 m is defined as 1 m2, and the area of a plane with any shape is also called 1 m2 if it is equivalent to the area of a square with a side length of 1 m.

Change history of area units

Area unit, a mathematical concept, refers to the unit for measuring the surface size of an object. The unit rate is 100, and the commonly used area unit is cm? (square centimeter) and m? (square meters), etc.

In ancient Egypt, the Nile River flooded once a year, bringing fertile silt to both banks, but also erasing the boundary signs between fields. After the water recedes, people have to calculate the area when they plan their fields again, so the concept of area gradually appears.

In autumn, the Nile recedes, leaving a layer of fertile silt on the land that has been soaked for several months. It is this layer of silt that enabled intensive agriculture to be realized and supported the prosperity and development of ancient Egypt. In the 5th century BC, Hippocrates of Hiosburg was the first to show that the area of a disk (the area surrounded by a circle) is directly proportional to the square of its diameter. As a part of orthogonality in Hippocrates' era, but the proportional constant has not been determined.