1.创设情境,引入课题师:上节课我们留了一个课外作业,让大家在网上、报纸上、杂志上搜集日常生活中一些比较大的数据,你们找到了吗?(学生自由发言,涉及内容是多方面的,有世界人口、中国的人口数,地球与太阳的距离,三峡工程的耗资,沙尘暴对农牧业的影响等.)师:现在我搜集了一些 1. Creating Situations and Introducing Problematic Teachers: In the previous class, we left a homework assignment for everyone to collect some of the larger data in daily life on the Internet, in newspapers, and in magazines. Did you find out? (Students speak freely, involving The content is varied, including the world’s population, the population of China, the distance between the Earth and the Sun, the cost of the Three Gorges Project, the impact of dust storms on agriculture and animal husbandry, etc.) Teacher: Now I have collected some