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培养学生逆向思维的品质极重要。在小学数学教学中,可从以下几个方面进行训练。①训练学生换角度理解题中的数量关系。如,有红花7朵,比黄花多3朵,问黄花有几朵?学生只要把“比黄花多3朵”,换个角度理解为“黄花比红花少3朵”,这时黄花的朵数就不难求出了。②训练学生善于逆用运算定律和性质。如,计算139×42+139×58逆用乘法分配律可将原式=139×(42+58)=139×100=13900③训练学生灵活地变通公式。如,把一张边长为15.7Cm的正方形铁皮焊成圆柱形烟筒,问这个烟筒的半径是多大(接头处忽略不计)?学生首先应该明确边长15.7cm就是烟筒的周长。根据圆周长公式
It is extremely important to cultivate the quality of students' backward thinking. In primary school mathematics teaching, you can train from the following aspects. ① training students to understand the relationship between the number of questions. For example, there are seven red flowers, yellow flowers more than 3, asked how many yellow flowers? Students as long as the “yellow flower more than 3”, from another point of view as “yellow flowers less than 3”, then the yellow flower Number is not difficult to find out. ② students are good at reversing the law and nature of the operation. For example, the calculation of 139 × 42 + 139 × 58 inverse multiplicative distribution law can be the original = 139 × (42 + 58) = 139 × 100 = 13900 ③ flexible training students flexibility formula. For example, a square 15.8cm long side of the metal welded into a cylindrical chimney, ask the radius of this chimney is (ignore joints)? Students should first of all be clear that the side length of 15.7cm is the chimney perimeter. According to the circumference formula