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一、提出表面相似而实质相异的问属进行比较。如: (1)一种药水是用药粉和水按照1:100配成的。要配制8080千克的药水,需要药粉多少千克? (2)一种药水是用药粉和水按照1:100配成的。在8080千克水中,需要药粉多少千克? 乍一看,这两道题几乎一样。药粉与水的比都是1:100,要求的都是药粉的千克数,题里都有8080千克这个数量。但仔细看,第(1)题是要配制8080千克药水,第(2)题是要在8080千克水中放药粉。“药水”与“水”是两个不同的概念,教师要引导学生辨析、比较。
First, put forward the similarities but different in substance to ask questions to compare. Such as: (1) a syrup is powder and water according to 1: 100 dubbed. To prepare 8080 kg of syrup, how many kilograms of powder required? (2) A syrup is used powder and water in accordance with the 1: 100 dubbed. In 8080 kilograms of water, how many kilograms of powder you need? At first glance, these two questions are almost the same. The ratio of powder to water is 1: 100, the required number of kilograms of powder, the problem has 8080 kg this number. But look carefully, the first (1) is to formulate 8080 kilograms of syrup, the first (2) is to put 8080 kilograms of water in the powder. “Syrup” and “water” are two different concepts, teachers should guide students to differentiate and compare.