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取近似值常用 的方法有三 种:四舍五入 法;进一法;去 尾法。小学数学课本中曾提到四舍五入法(九册课本)和进一法(十二册课本),可是没有提到什么叫“去尾法”,但是在十二册课本的例题和练习题中多次出现用“去尾法”取近似值的内容,如果不给学生讲清什么是“去尾法”,那么就会出现取近似值的结果不符合实际的情况。为避免这种错误,应在适当的例题中给学生补充这个内容。 在“圆柱的体积”一节有这样一道例题:一个圆柱形水桶,从里面量底面直径是30厘米,高40厘米。这个水桶的容积是多少?
There are three commonly used methods to take approximations: rounding; entering a law; going to the tail. Primary school mathematics textbooks have mentioned rounding (nine textbooks) and one method (twelve textbooks), but did not mention what is meant by the “tail to tail method”, but in 12 volumes of textbook examples and exercises more Appear with the “to the tail method” to take the approximate value of the content, if you do not tell the students what is the “tail method”, then there will be approximation results do not fit the actual situation. To avoid this error, students should be supplemented with the appropriate examples. In the “Cylindrical Volume” section there is an example: a cylindrical bucket with a diameter of 30 cm and a height of 40 cm from the bottom. What is the volume of this bucket?