五年制小学数学课本第五册,有一道思考题:运用加法的运算定律,算出1+3+5+……+17+19和2+4+6+……+18+20的得数。这是中高年级数学兴趣小组活动的好题材。如果使用得当,将有助于学生各种能力的培养,也有利于中小学数学教学的衔接。指导学生解答时可分几个步骤: (一)认真读题。带有省略号的算式,学生初次接触,感到陌生,需要一定的想象力。教学时可先要求学生把题目补写完整,使他们理解式子的含义,熟悉算式的书写形式,做好从具体到抽象的过渡工作,促进学生的思维过程从“有限”到“无限”的飞跃。(事实上把省略号移到算式末尾,就表示无 Five-year primary school mathematics textbook fifth book, there is a question of thinking: the use of law of addition operation, calculate 1 +3 +5 + ... +17 +19 and 2 +4 +6 + ... +18 +20 the number of . This is a good topic for middle and senior math interest group activities. If used properly, will help students develop various abilities, but also conducive to the convergence of primary and secondary mathematics teaching. Guide students to answer can be divided into several steps: (A) serious reading questions. With the ellipsis formula, students first contact, feel strange, you need some imagination. When teaching, students should first ask the students to make up the questions so that they can understand the meaning of formulas, be familiar with the writing forms of formulas, do the transition from concrete to abstract, and promote the students' thinking process from “limited” to “unlimited” leap. (In fact, the ellipsis moved to the end of the formula, it means no