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教学多边形的面积之后,很多教师都曾让学生解答过类似下面这样的题目:一个平行四边形的一组邻边的长分别是5厘米和3厘米。小明在这个平行四边形内画了一条4厘米的高,你知道这个平行四边形的面积是多少平方厘米吗?学生解答上面这道题的方法主要有两种,一种是5×4=20(平方厘米),另一种是3×4=12(平方厘米)。而且大部分学生都说不清列式的依据,只是从已知条件中选择一个“底”的数据与“高”的数据
After teaching the area of the polygons, many teachers have asked students to answer questions such as the following: A parallelogram of a group of adjacent length of 5 cm and 3 cm respectively. Xiao Ming draws a 4cm high in this parallelogram. Do you know how many square centimeters this parallelogram is? There are two main ways that students can answer the above question. One is 5 × 4 = 20 (square centimeters ) And the other is 3 × 4 = 12 (square centimeters). And most of the students can not tell the basis of the column type, but from the known conditions, select a “bottom ” data and “high ” data