笔者在对我省“全日制普通高级中学教科书《数学》第一册 (上 ) ( 2 0 0 3年审查通过 ) P98～ 99的例 2进行备课时感觉有点困惑 ,原题如下 :用水清洗一堆蔬菜上残留的农药 ,对用一定量的水清洗一次的效果作如下假定 :用 1个单位量的水可清除蔬菜上残留农药量的1 /2 ,用水越多 , The author feels a bit confused when he prepares lesson 2 of the province’s “full-time ordinary high school textbook mathematics” book 1 (top) (2003 review passed) P98 to 99 Example 2, the original question is as follows: The residual pesticides on piles of vegetables are assumed to be washed once with a certain amount of water. The following assumptions are made: 1 unit of water can be used to remove 1/2 of the amount of pesticides remaining on the vegetables. The more water is used,