本课是在学生学习了求整数的近似数的基础上进行学习的,目的是让学生学会用四舍五入法求小数的近似数,并能把大数改写成用“万”或“亿”做单位的数,再求近似数。我充分利用导学案,在学习之前,我先根据学生情况让学生复习求整数的近似数的方法——“四舍五人法”。在求小数近似数的过程中,我重点把握了三个教学重难点,即:1.理解“保留几位小数,精确到什么位,省略什么位后面的尾数”这些要求的含义:2.在 This lesson is based on the student learning the approximate number of integers to learn based on the purpose of allowing students to learn the approximate number of decimals using the rounding method and can rewrite the large number into the use of “To do the number of units, and then find the approximate number. I take full advantage of the guide case, before I learn, I first let students review the approximation of the integer number of students - ”round and round method “. In the process of finding a fractional approximation, I focus on three teaching difficulties, namely: 1. Understand ”Retain a few decimals, what exact place, omit the mantissa behind what " The meaning of these requirements: 2 .in