在与密度有关的计算题中 ,常常涉及取近似值 ,其中多是用“四舍五入法”。但这往往又是一个陷井 ,如果不加思考 ,不联系实际 ,一味地采用“四舍五入法” ,就会落入“圈套” ,使计算结果脱离实际 ,造成错误。下面是在与密度相关的计算中 ,取近似值出错的例子。1　用“进一法”取 In density-related calculation problems, it often involves taking approximate values, most of which use the “round-off method.” However, this is often a trap. If you do not think about it, do not relate to reality, and blindly adopt the “round-off approach,” you will fall into the “snapping,” making the calculation result out of reality and causing mistakes. The following is an example of an erroneous approximation to a density-related calculation. 1 Use the “into a method” to take